Mandate 'contains-issue-number' in PR's body

[itachi3]

If PR body contains some random text, zappr doesn't complain about 'contains-issue-number'

If it is empty or contains some keywords like refer/close then it does complain

Ideally it should complain in all cases when the issue number is missing.

[fokusferit]

@itachi3 could you please provide a bit more description with clear steps. Also some screenshots are always helpful to fully understand the issue. I think I understand but would prefer some more information first.