Fix typos and write style

[raethlein]

What kind of change does this PR introduce?

• [ ] Bugfix
• [ ] New Feature
• [ ] Feature Improvment
• [ ] Refactoring
• [X] Documentation
• [ ] Other, please describe:

Description:

Fix some wording and improve general quality of writing by using standardized names (e.g. Github -> GitHub, Dockerhub -> Docker Hub, ...) in markdown files and markdown generation.

Checklist:

• [X] I have read the CONTRIBUTING document.
• [X] My changes don't require a change to the documentation, or if they do, I've added all required information.