Add GHA workflow to run the test app

[kraenhansen]

We might be able to take some inspiration from:

• the react-native-test-app repo: https://github.com/microsoft/react-native-test-app/blob/trunk/.github/workflows/build.yml
• Realm JS
• mocha-remote
• a new cross-platform-testing-library
• we might want to simply send an HTTP request once the app is done testing

[kraenhansen]

This was completed with #133