Add changelog to releases

[florianmutter]

It would be very helpful if the release would contain a change log. This would make updating the action way easier and avoid unexpected changes from being applied and breaking pipelines.

[nicksnyder]

This GitHub action just follows the releases for the Buf CLI, so the relevant changelog is here:
https:/bufbuild/buf/blob/main/CHANGELOG.md

We did release some big improvements to the Buf CLI recently, but we took many steps to ensure backward compatibility. If you are having compatibility issues, please report them in https:/bufbuild/buf and we can investigate.

Going to close this issue since we don't plan on having a separate CHANGELOG for this action.

[florianmutter]

Good to know. My suggestion is then to copy the changelog of buf cli into the buf action release