Update modules/authentication/proc-enabling-authentication-with-github.adoc

Author: themr0c

modules/authentication/proc-enabling-authentication-with-github.adoc

@@ -169,6 +169,14 @@ To enable GitHub integration with another authentication provider you have alrea
 .`app-config-rhdh.yaml` fragment with mandatory fields to enable integration with GitHub and use a different authentication provider
 [source,yaml]
 ----
+auth:
+  environment: production
+  providers:
+    github:
+      production:
+        clientId: ${AUTH_GITHUB_CLIENT_ID}
+        clientSecret: ${AUTH_GITHUB_CLIENT_SECRET}
+    __<your_other_authentication_providers_configuration>__
 integrations:
   github:
     - host: ${GITHUB_HOST_DOMAIN}
@@ -180,6 +188,7 @@ integrations:
           webhookSecret: ${GITHUB_WEBHOOK_SECRET}
           privateKey: |
             ${GITHUB_PRIVATE_KEY_FILE}
+signInPage: __<your_main_authentication_provider>__
 ----
 ====