added more FAQ

Author: dikshant-devops

docs/faq.md

@@ -81,6 +81,12 @@ or remove users as needed.
 To move to Pro, login to CodeRabbit and navigate to the Subscription page.
 Click on **End Trial and Start Pro Plan** to end the trial and move to the Pro plan.
 
+#### How to Add or Update Your Billing Email
+
+To add or update your billing email, navigate to the Subscription page and 
+select Manage Subscription > **Billing Address**. Enter your email address in the 
+Email field and click Update to save your changes.
+ 
 ### Usage and Configuration
 
 #### Can CodeRabbit review my existing PRs after integrating it?
@@ -151,3 +157,15 @@ If you have further questions or need additional information, please check out
 our [Support](./about/support.md) page for more details.
 
 :::
+
+#### Unable to View Repositories in GitLab
+
+If you cannot view repositories in the CodeRabbit UI, please ensure that you
+are added as a Developer in the main group for GitLab Cloud or in the primary
+group for Self-Hosted GitLab.
+
+#### Unable to Enable Repositories in GitLab
+
+If you’re having trouble enabling the GitLab Repositories toggle, confirm that
+you have Maintainer access in the main group for GitLab Cloud or in the 
+primary group for Self-Hosted GitLab.