Add CI to Project

It'd be really nice to have some CI on our project. Let's use Azure Pipelines to do that for us.

For this issue, don't do anything fancy regarding CD or branch-specific tasks, just create a CI pipeline which runs the same task on all branches and PRs. Here is what should be done:

• Build the debug variant of the app with assembleDebug
• Save the generated, unsigned APK as an artifact