Link to providers in readme.
Link to providers in readme.

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