Rollup merge of #76516 - pietroalbini:github-releases, r=Mark-Simulacrum

Rollup merge of #76516 - pietroalbini:github-releases, r=Mark-Simulacrum

Enable GitHub Releases synchronization

This PR enables the triagebot feature to automatically populate [GitHub Releases](https://github.com/rust-lang/rust/releases) for this repository based on the changelog. See https://github.com/rust-lang/triagebot/pull/811 for the implementation of this feature on triagebot's side, and more insights on how it works.

Note: once this lands people subscribed to the ~~firehose~~ rust-lang/rust repository will probably receive a ton of notifications for all the releases being created, but this should be a one-time thing.

r? @Mark-Simulacrum
cc @rust-lang/release