Collection of rules for linting

[ralf401]

This is a collection of thinks which come to my mind while writing the documentation. At some point we can talk about them and decide which one to include.

• External links with added {target=_blank}
• Check if dead internal links are present
• Special keyboard keys like enter or ctrl which have the [[ ]] markup => enforce small or capital letter at the beginning?
• Code blocks without $ at the beginning
• Headings only by using #