ShutterSoundToggle v1.0

Sign builds and publish tagged releases

CI signs with the public AOSP test key so that its APKs install, and
checks the fingerprint so that it can never hand out the release key's
signature. A v* tag builds with the release key from the Actions
secrets and checks that fingerprint before attaching the APK to a
GitHub release, since an APK signed by any other key cannot update an
existing install.

versionCode follows the run number so that each release can be
installed over the previous one.