[update] Update vanillajs.md to use redirect mode
[update] Update vanillajs.md to use redirect mode

Update tutorial to explain how to implement redirect mode instead of popup mode.
hamzawi06/docs,Annyv2/docs,hamzawi06/docs,sandrinodimattia/docs,sandrinodimattia/docs,jeffreylees/docs,jeffreylees/docs,yvonnewilson/docs,Catografix/docs,auth0/docs,Catografix/docs,miparnisari/docs,yvonnewilson/docs,hamzawi06/docs,khorne3/docs,jeffreylees/docs,auth0/docs,Annyv2/docs,Catografix/docs,Annyv2/docs,yvonnewilson/docs,sandrinodimattia/docs,auth0/docs,khorne3/docs,khorne3/docs