Setup GitHub Actions for tests

[MGaetan89]

Now that @Zardozz has started to add some tests to the project, it's worth having a CI to ensure that new changes don't break the existing code.
For the moment, the workflow:

• builds the project
• checks that the sample app still compiles
• runs the tests on emulators:
  • with API 15 (API 14 is not supported by the action I use)
  • with API 29 (the target SDK the project)

A sample output can be seen here: https://github.com/MGaetan89/TableView/actions/runs/497047998

You might have to enable GitHub Actions in the project settings for this to work.