Add nginx auth_request config to README
Add nginx auth_request config to README

tamsky/oauth2_proxy,sonatype/google_auth_proxy,hayatalish/google_auth_proxy,sonatype/google_auth_proxy,coreos/oauth2_proxy,andyuc88/oauth2_proxy_azure,bitly/oauth2_proxy,kalibrr/oauth2_proxy,ploxiln/oauth2_proxy,kalibrr/oauth2_proxy,vend/oauth2_proxy,hayatalish/google_auth_proxy,revinate-docker/oauth2_proxy,bitly/oauth2_proxy,jehiah/oauth2_proxy,ploxiln/oauth2_proxy,bitly/google_auth_proxy,kbudde/oauth2_proxy,ITNG/oauth2_proxy,Shopify/google_auth_proxy,ITNG/oauth2_proxy,snormore/oauth2_proxy,snormore/oauth2_proxy,vend/oauth2_proxy,bitly/google_auth_proxy,revinate-docker/oauth2_proxy,andyuc88/oauth2_proxy_azure,kbudde/oauth2_proxy,Shopify/google_auth_proxy,jehiah/oauth2_proxy,tamsky/oauth2_proxy,18F/oauth2_proxy,18F/oauth2_proxy,Shopify/google_auth_proxy,coreos/oauth2_proxy