add german translation and dependence

[gras64]

No description provided.

[LinusSkucas]

Hi @gras64 ! Thanks for doing the translations and for adding the requirements. I was able to solve the requirements problem, and I am still able to use manifest.yml, so adding a requirements file won't be necessary.
Also, the translations I don't think copy over to the translate site, so people would have to translate there, and over-write the translations here. I'm also in the process of adding the calling feature, which also adds many dialogs that need to be translated, and I've updated some of the ones that you've already translated.

So what do you think we should do? I'm inclined to close this pr, and have people do the translations on the translate site. I hope to submit this by the end of July, and once translations come in, I'm usually pretty good about merging them and resubmitting.