German Translation (de_DE)

A couple of hints regarding the German translation:

• The project organizers prefer to get one pull request per language. Therefore we decided to collaborate over in this fork: https://github.com/max-dau/Translate (please ping @max-dau here on GitHub or @maxdau on Discord to be added there as contributor)
• You can find more details about how we want to work on the translation in the wiki over there: https://github.com/max-dau/Translate/wiki/