Further Update README.md

[Jonas-Sander]

Some ideas:

• General introduction
  • What does the app do? (Screenshots, Videos, etc.)
  • In a sentence: How did the app came to be?
  • Link to app (inform that it is currently only in German)
• What to do if one finds a bug or has an idea for a feature (see Plan on where bug reports and feature requests go #29)
• How to contribute - reference to CONTRIBUTING.md (see Create documents explaining how to contribute and what to look out for. #28)
• What one should do if one finds a security bug
• Links to our social media etc

[Jonas-Sander]

Add a Discord batch?