Two more themes + Bump for release V1.22.

[pserwylo]

Fixes #57.

Two themes added: Pastel + Rainbow. Refactored the way themes work to make it easier to define key colours.

This release will also include the dutch translations from #61.

[pserwylo]

Thanks for the feedback as always @juleskers. Hope your first day back was fine. I'll tag this so F-Droid can build.

[juleskers]

You're welcome! thanks for putting up with my obsession about colors/colours 😉 (🇦🇺Australian, nice!)