Long, formatted description for rules supporting markup

[DirkMahler]

I, as a rule provider
would like to add a long formatted description to a rule containing code examples
to that a developer may get a better understanding of "invalid" and "valid" code (similar to SonarQube)

So there should be two descriptions:

• a short plain text descriptions which already exists

• a long description which supports markup like Asciidoc which may contain code snippets and can be rendered

• We got a final feedback from the reporting user (if applicable)

• Unittests have been written (if applicable)

• Integration tests have been written (if applicable)

• Test coverage is the same or even better then before (if applicable)

• Documentation has been written (if applicable)

• Added a note on the new feature to the release notes (if applicable)