tox.ini: Check commit message guidelines using commit-message-validator
tox.ini: Check commit message guidelines using commit-message-validator

Bug: T109119
Change-Id: Ifa48bdcd3f89c325271f4e623973f52e991d5c00

wikimedia/pywikibot-core,PersianWikipedia/pywikibot-core,happy5214/pywikibot-core,npdoty/pywikibot,npdoty/pywikibot,magul/pywikibot-core,wikimedia/pywikibot-core,magul/pywikibot-core,happy5214/pywikibot-core