chore: setup a github action to create releases

[rickeylev]

This defines up a GitHub action to create a Github release and BCR configs for the Publish
To BCR app.

Creating a X.Y.Z tag will trigger the action.

[rickeylev]

@tetromino I saw you created release so quick, but didn't have any automation set up. So thank you for being so fast!

I can't test this end-to end, but I think this is the basic for automating releases. You (or whoever is listed as fixedRelease) needs to setup the Publish to BCR app to fully automate that part.

[tetromino]

Thank you very much for the PR, this could reduce a lot of toil! I will need to review in detail, but after a quick look, the main thing I'd like to change is to use custom changelog text in release notes instead of automatically generated one. (Probably by prepending the latest manually-written CHANGELOG.md entry to the release notes.)