chore: script to create a Rust release (#759)

For now, keep things simple such that we never update the `version` in
the `Cargo.toml` for the workspace root on the `main` branch. Instead,
create a new branch for a release, push one commit that updates the
`version`, and then tag that branch to kick off a release.

To test, I ran this script and created this release job:

https://github.com/openai/codex/actions/runs/14762580641

codex-rs/Cargo.toml

@@ -11,7 +11,7 @@ members = [
 ]
 
 [workspace.package]
-version = "0.0.2504301132"
+version = "0.0.0"
 
 [profile.release]
 lto = "fat"