[IMPROV] docs: Mention that Python 3 is supported
[IMPROV] docs: Mention that Python 3 is supported

Change-Id: Ie8973a90485a1bd6f05de383e5dd8ea902f6e713

TridevGuha/pywikibot-core,jayvdb/pywikibot-core,xZise/pywikibot-core,magul/pywikibot-core,happy5214/pywikibot-core,hasteur/g13bot_tools_new,Darkdadaah/pywikibot-core,valhallasw/pywikibot-core,trishnaguha/pywikibot-core,magul/pywikibot-core,h4ck3rm1k3/pywikibot-core,wikimedia/pywikibot-core,npdoty/pywikibot,happy5214/pywikibot-core,PersianWikipedia/pywikibot-core,VcamX/pywikibot-core,smalyshev/pywikibot-core,icyflame/batman,Darkdadaah/pywikibot-core,emijrp/pywikibot-core,wikimedia/pywikibot-core,hasteur/g13bot_tools_new,h4ck3rm1k3/pywikibot-core,jayvdb/pywikibot-core,darthbhyrava/pywikibot-local,hasteur/g13bot_tools_new,npdoty/pywikibot