CI: publish Kotlin-name stubs for Compose 1.11.1 as a build artifact #32

pythonx-compose (#12) consumes the binder's Kotlin-name stubs for the real Compose jars, but cannot run this repository's Gradle build. Publish them from CI: a job that runs the stub task over the Compose 1.11.1 artifacts and uploads pythonStubs as a workflow artifact (and attaches it to tags).

Completion: a develop push produces a downloadable stubs artifact; its README names the Compose version and the producing commit.