Fix: Explicitly define in the GitHub action the Api, Client, and wwwroot

[csharpfritz]

The current version of the template relies on these being discovered by the build action. Sometimes this is not discovered properly so I suggest we explicitly configure them by default

[aaronpowell]

Do you mean for the build process itself?

Presently we're unable to ship the YAML build file within a repo in a reliable manner, as it requires some access tokens that Azure generates for you (and you're unable to generate yourself).

A better place to raise that sort of an issue would be on https://github.com/Azure/static-web-apps/issues