pull request submission trigger to verify the format

Add a trigger on pull request submission to verify the format of the lists/ files if the file was changed.

The check consists of counting all lines that start with

^[[:space:]]*\*

and compare these to the count of lines that matches

^[[:space:]]*\*[[:space:]]+\[[^]]+\]\(https://github\.com/[a-zA-Z0-9_-]*)$

It must match.