Document test decorators.
Document test decorators.

Documentation regarding mock.patch, tests.aspects.require_modules,
unittest.skipIf and unittest.skipUnless is added to the README file.

Bug: T152068
Change-Id: I335323a1704a9912dbc39bcec8042ae8ee706234

hasteur/g13bot_tools_new,PersianWikipedia/pywikibot-core,wikimedia/pywikibot-core,hasteur/g13bot_tools_new,hasteur/g13bot_tools_new,magul/pywikibot-core,wikimedia/pywikibot-core,Darkdadaah/pywikibot-core,happy5214/pywikibot-core,magul/pywikibot-core,happy5214/pywikibot-core,Darkdadaah/pywikibot-core,jayvdb/pywikibot-core,jayvdb/pywikibot-core,npdoty/pywikibot,npdoty/pywikibot