update intro and header, add warning for search (#6451)
update intro and header, add warning for search (#6451)

Got a request from infra to advise against searching for users inside a rule
jeffreylees/docs,auth0/docs,jeffreylees/docs,yvonnewilson/docs,yvonnewilson/docs,auth0/docs,jeffreylees/docs,auth0/docs,yvonnewilson/docs