Provide CI build results in pull-requests

[ochosi]

To enable better reviewing of PRs that refactor or restructure the guides (e.g. #86) it would be nice to add a step to our GitHub Actions workflow to provide the results of the build that happens anyway to the reviewer.

This is possible through the native archiving step (see https://docs.github.com/en/actions/using-workflows/storing-workflow-data-as-artifacts).
One limitation is that the archive is not available until after the workflow is done so you cannot easily post a comment with a link to the archive to the pull request.