This PR add several features to release automation:
1. The existing tag-release job has an output that indicates whether the
triggering commit
is a release (i.e. whether it matches the regex)
2. The new followup job runs a new script which fetches the recent
emscripten-releases
revisions, reads the DEPS file from the 'latest' release in
emscripten-releases-tags.json
to find the corresponding emscripten revision and writes it into the
environment
2. The final step reads the emscripten revision from the environment and
creates a
workflow_dispatch event to run the tag-release.yml job on the emscripten
repo
The action runs the existing create_release.py script in a new mode
created for github actions. Rather than using local git commands, it
uses a public action for creating a PR in the repository. The action can
be triggered from the website or via the CLI tool, for example
gh workflow run create-release.yml -R emscripten-core/emsdk -F
lto-sha=abc123 -F nonlto-sha=234567
