Release automation

[JohnTitor]

Currently, I do release manually. But I'd like to do continuous release as it depends on a specific nightly version, and this could be done by GHA, I think.

[dario23]

what should trigger a new release? merged commit that changes the rust-toolchain file? or just any merged commit? nightly if anything was merged that day? is there a way to tell bors to trigger a release, similar to the rollup arg? otherwise i guess we can build a github action on a label do-release that triggers a release once a pull request with that label gets merged.

[JohnTitor]

bors doesn't handle any release but merges PRs. I think we can listen to adding a git tag event and trigger the workflow. More automation e.g. auto-incrementing version number would be possible but it's overkill here, I feel. I just don't want to do a release on my local (at least for now).
Note that this will need us to set the crates.io token, I'm going to ask the infra team once it's ready.