Add Meetup provider subspec.
Add Meetup provider subspec.

tofaruk/SimpleAuth-1,AlexanderMazaletskiy/SimpleAuth,jiakai-lian/SimpleAuth,machelix/SimpleAuth,hoanganh6491/SimpleAuth,sburavtsov/SimpleAuth,adamjmcgrath/SimpleAuth-1,tipbit/SimpleAuth,calebd/SimpleAuth,martinpilch/SimpleAuth,hyperspacemark/SimpleAuth