release docs: Add stylo section

[jschwe]

Add instructions for requesting a stylo release

[jschwe]

CC @Loirooriol, not sure if you expect to handle the release yourself, or if we should add docs on how to create a version bump PR for stylo (including using cargo-semver checks, and figuring out which crates need a bump)? If you'd like that perhaps you could add a sentence or two for that, since I don't quite recall all the details.

[Loirooriol]

It's basically:

• In Cargo.toml, raise version in [workspace.package].
• For the standalone crates that have their own version, use git diff <prev> --stat to see what changed since last time. If there was some change, then raise the version. This needs to happen both in the [workspace.dependencies] of the root Cargo.toml, and in the [package] of the Cargo.toml of the crate being bumped.
• The major version is currently 0. And raising just the patch version is problematic if the changes weren't backward compatible. So I just raise the minor version.