Create workflow for contributing new topics

[jhorzek]

• [x] Do we want to just commit to the main branch?
• [x] Should the website be update on commit to main? This take a lot of resources but it's a lot easier than the manual update. However, it only makes sense if everyone works on a branch.
• [x] Should we protect the main branch so that commits to main require a review from other project members?

[jhorzek]

Der Main Branch wird protected sein, sobald das Projekt public ist. Die Webseite soll automatisch erstellt werden.