Replace CircleCI with GitHub Actions

[rob-luke]

Currently I build all docs with GitHub Actions. And the webpage is created using GH actions.

However, to easily view docs in PRs I use circleci as you can browse the temporary docs using a web browser. (you can view the GH actions artefact, but requires downloading a zip and extracting).

Once you can view GitHub Actions artefacts in browser I will switch to this.

See actions/upload-artifact#14

[larsoner]

There is a project @agramfort knows about (I can't remember the name) that builds docs with GH Actions, then uses CircleCI just to download and expose them as artifacts IIRC. @agramfort which one was it?

[rob-luke]

I believe this is it https://github.com/braindecode/braindecode/blob/master/.circleci/config.yml

[larsoner]

Closing as wontfix :)