Consider publishing a beta package

[desyncr]

Currently we've only beta releases. Once we release a production ready app we must have a way to release beta/test updates through Fdroid.

Review fdroid beta/production channels support. Some releases updates can be ignored with https://f-droid.org/docs/Build_Metadata_Reference/#UpdateCheckIgnore. This mean we can setup 2 packages, 1 for production and 1 for beta/testing.