Add Ruby release instructions, update version updates (sigstore#90)

* Add Ruby release instructions

Same as python/rust/ts

Signed-off-by: Hayden B <hblauzvern@google.com>

* Update RELEASE.md

Signed-off-by: Hayden B <hblauzvern@google.com>

* Update RELEASE.md

Signed-off-by: Hayden B <hblauzvern@google.com>

---------

Signed-off-by: Hayden B <hblauzvern@google.com>

RELEASE.md

@@ -62,6 +62,10 @@ Checklist prior to releasing:
    `version` matches the targeted release.
 1. Update [package.json](gen/pb-typescript/package.json) so the
     `version` matches the targeted release.
+1. Update [version.rb](gen/pb-ruby/lib/sigstore_protobuf_specs/version.rb) so the
+   `version` matches the targeted release.
+1. Update [Cargo.toml](gen/pb-rust/Cargo.toml) so the
+   `version` matches the targeted release.
 
 When all of the above are set, prepare for release by creating a tag
 with the following pattern: `vX.Y.Z` and push to the repository. Bonus
@@ -92,6 +96,12 @@ Prepare a tag with the following pattern `release/python/vX.Y.Z` and
 push it. The [workflow](.github/workflows/python-release.yml)
 will automatically start.
 
+### Ruby
+
+Prepare a tag with the following pattern `release/ruby/vX.Y.Z` and
+push it. The [workflow](.github/workflows/ruby-release.yml)
+will automatically start.
+
 ### Rust
 
 Prepare a tag with the following pattern `release/rust/vX.Y.Z` and