Xcamera

- Increase test coverage to 93%
- Move PythonActivity from 'kivy' after 'renpy' drop, closes 15, refs 16
- Introduces GitHub actions, refs 18
- Also tests against Python 3.8, refs 19
- Android build CI, refs 20
- Uploads APK artifact, refs 21
- Automates PyPI releases from CI, refs 22
- Bumps to kivy post 2.0.0rc2 on Android, refs 23

- Setup coverage testing
- Runtime camera permission check, refs 5
- Publish `xcamera` demo binary, refs 9
- Add Python3.7 support, refs 13

- Move to new garden layout
- Setup Docker testing
- Split kvlang file from Python code
- Setup Continuous Integration testing, refs 1
- Setup linting, refs 2
- Unit tests `platform_api` module, refs 3
- Publish to PyPI, refs 4
- Introduce `Makefile`, refs 8

- Initial release before revamp