Add GitHub Actions workflow for docs

[CaptainIRS]

In this PR:

• GitHub actions workflows are added to the gh-pages branch
• Issues pointed out by DCI lint are fixed for the latest and vNext docs

This is done because according to GitHub Docs:

The following steps occur to trigger a workflow run:
...
2. GitHub searches the .github/workflows directory in your repository for workflow files that are present in the associated commit SHA or Git ref of the event.

So, the workflow file is expected to be present in the gh-pages branch for it to run.

[davidkel]

one minor change on the workflow name, but looks good

[davidkel]

LGTM