feat(schemas/github-action): support composite run steps

[ngraef]

This PR updates the github-action json schema with support for the new composite run steps and pre*/post* scripts. It also updates all $comment links to GitHub's new docs site.

[madskristensen]

Thanks

[amis92]

I'm not sure who's the "owner" of this file, and if there's any - but I found, when building my composite action, that outputs.<output-id>.value is not recognized.

This property is documented at https://docs.github.com/en/actions/creating-actions/metadata-syntax-for-github-actions#outputs-for-composite-run-steps-actions

I'd gladly make a PR, but I don't really know much about json schemas, and I'm not sure how to link using: composite with outputs, as they are in different "root" properties.

[madskristensen]

@ngraef any tips regarding implementing the behavior @amis92 is mentioning? Sounds like a bug in the schema

[ngraef]

Thanks for pointing that out, @amis92. I can get the schema updated.