Clarify warning & fix line number

[CleanCut]

#107 established that this warning is intended to advise users to set the type for a group. This PR is to:

• Clarify the message, including a link to the documentation for the type.
• Fix the line number (previously the line number was always 5)

From syntax.md...

• type, optional enum, defaults to span (with a warning if not present).

I would love to add some language to this ☝🏻 section of the syntax.md document, further explaining what a group's type field means. Unfortunately, I don't know what it means. Could anyone suggest some further explanation?

[CleanCut]

Before:

Using default SPAN type for semantic convention 'browser' @ line 5
Using default SPAN type for semantic convention 'cloud' @ line 5
Using default SPAN type for semantic convention 'aws.ecs' @ line 5
Using default SPAN type for semantic convention 'aws.eks' @ line 5
Using default SPAN type for semantic convention 'aws.log' @ line 5
Using default SPAN type for semantic convention 'container' @ line 5
Using default SPAN type for semantic convention 'deployment' @ line 5
Using default SPAN type for semantic convention 'device' @ line 5
Using default SPAN type for semantic convention 'faas_resource' @ line 5
Using default SPAN type for semantic convention 'host' @ line 5
Using default SPAN type for semantic convention 'k8s.cluster' @ line 5
Using default SPAN type for semantic convention 'k8s.node' @ line 5
Using default SPAN type for semantic convention 'k8s.namespace' @ line 5
Using default SPAN type for semantic convention 'k8s.pod' @ line 5
Using default SPAN type for semantic convention 'k8s.container' @ line 5
Using default SPAN type for semantic convention 'k8s.replicaset' @ line 5
Using default SPAN type for semantic convention 'k8s.deployment' @ line 5
Using default SPAN type for semantic convention 'k8s.statefulset' @ line 5
Using default SPAN type for semantic convention 'k8s.daemonset' @ line 5
Using default SPAN type for semantic convention 'k8s.job' @ line 5
Using default SPAN type for semantic convention 'k8s.cronjob' @ line 5
Using default SPAN type for semantic convention 'os' @ line 5
Using default SPAN type for semantic convention 'process' @ line 5
Using default SPAN type for semantic convention 'process.runtime' @ line 5
Using default SPAN type for semantic convention 'service' @ line 5
Using default SPAN type for semantic convention 'telemetry' @ line 5
Using default SPAN type for semantic convention 'webengine_resource' @ line 5

After:

Please set the type for group 'browser' on line 2 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'cloud' on line 2 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'aws.ecs' on line 2 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'aws.eks' on line 2 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'aws.log' on line 2 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'container' on line 2 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'deployment' on line 2 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'device' on line 2 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'faas_resource' on line 2 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'host' on line 2 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'k8s.cluster' on line 2 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'k8s.node' on line 13 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'k8s.namespace' on line 29 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'k8s.pod' on line 40 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'k8s.container' on line 56 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'k8s.replicaset' on line 76 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'k8s.deployment' on line 92 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'k8s.statefulset' on line 108 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'k8s.daemonset' on line 124 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'k8s.job' on line 140 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'k8s.cronjob' on line 156 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'os' on line 2 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'process' on line 2 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'process.runtime' on line 73 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'service' on line 2 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'telemetry' on line 2 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups
Please set the type for group 'webengine_resource' on line 2 - defaulting to type 'span'. See https://github.com/open-telemetry/build-tools/blob/main/semantic-conventions/syntax.md#groups

[Oberon00]

I think you know the meaning of the type, since you suggested the correct types in the semantic conventions.
There are also some technical consequences since certain fields can only be set for certain types, e.g. name can only be set for type: event.