Aa-sov-timer

Added

- Spanish translation

Fixed

- Bootstrap CSS fix

Added

- Footer to promote help with the app translation

Added

- Ukrainian translation prepared. Not translated yet, [need translators](https://github.com/ppfeufer/aa-sov-timer/blob/master/CONTRIBUTING.md#translation).

Changed

- Moved the build process to PEP 621 / pyproject.toml

Added

- Russian translation

Added

- German translation