deprecate annotations package

[tomwayson]

Annotations are being replaced by discussions.

We have not added any features to annotations for many months, it's essentially in maintenance mode. Yet, new versions are released regularly b/c we don't use lerna's independent versioning (that's a subject for another issue).

We're also planning on consolidating other packages in #306 so I think it's a good idea to establish a pattern for how we deprecate a package. Mainly I want to get the deprecated code out of our build, test, and publish pipelines. Of course we could just delete the package, but I think it would be better to move the package's source code out of the packages folder and into a new root-level folder (i.e. deprecated) w/in the monorepo. This will prevent the tooling from building/testing/releasing the package with the others, but still allow us to easily review the old source code, or make maintenance updates if needed.

Additionally, we should:

• add a deprecation message to package README
• cut one final release w/ ^^^
• mark the package as deprecated in the npm registry

[tomwayson]

it's a good idea to establish a pattern for how we deprecate a package

In #654 I added a Deprecated Packages section of the README that can link to the last commit that had that package, so that we can have easy access to the source code and safely remove the files from master.