Set applicationId to com.subtracks and add a GitHub Actions workflow
that, on a v* tag, builds and signs the release APK and AAB, creates
the GitHub release with the APK, and uploads the AAB to Google Play.
Release notes come from the matching metadata changelog.
Signing reads the keystore from the environment
(RELEASE_KEYSTORE, RELEASE_KEYSTORE_PASSWORD, RELEASE_KEY_ALIAS,
RELEASE_KEY_PASSWORD) and falls back to the debug key locally.
