Add german translation

[florianholtgrefe]

Because PR #1326 has not been updated since October last year, i've created this new PR with a full german translation.

[vercel[bot]]

@florianholtgrefe is attempting to deploy a commit to the prafull 's projects Team on Vercel.

A member of the Team first needs to authorize it.

[nxglabs]

@raktima-opensignlabs please review this and merge.

[natemate90]

@andrew-opensignlabs / @pravinOpenSign / @prafull-opensignlabs This is a great contribution, the missing German translations are preventing me to start using OpenSign 😁 Would be great if you could approve the above PR. Many thanks for your great work!