Docs: Make build automation docs more beginner friendly

[academo]

We have docs on how to use github actions pipelines for automated plugin packages and signing but the guide is a bit short for more beginner users of github actions.

https://grafana.com/developers/plugin-tools/publish-a-plugin/build-automation

We should expand this guide to include more beginner-friendly information.

Considering now all of the plugins are scaffolded with github action workflows we can add direct instructions of how to use them if they are using github for their repository.