docs: Add documentation for managing repository access after GitHub App installation (#144)

Co-authored-by: promptless[bot] <179508745+promptless[bot]@users.noreply.github.com>

Author: promptless[bot]

docs/integrations/github.mdx

@@ -18,6 +18,23 @@ Promptless integrates with Github through our official Github App, providing sec
 4. Verify that Promptless is connected in the integrations page. 
 <img src="/img/integrations-complete.png" alt="Integrations Page" style={{width:"800px", display: "block", margin: "0 auto", boxShadow: "0 4px 8px rgba(0, 0, 0, 0.1)", marginBottom: "20px"}} />
 
+## Managing Repository Access After Installation
+
+After the initial installation, you may need to add new repositories or modify which repositories Promptless can access. You can manage this directly through your GitHub organization settings:
+
+1. Navigate to your GitHub organization settings
+2. Go to "Third-party Access" → "GitHub Apps" 
+3. Find "Promptless" in the list and click "Configure"
+4. In the "Repository access" section, you can:
+   - Switch between "All repositories" and "Only select repositories"
+   - Add or remove specific repositories using the "Select repositories" dropdown
+   - Remove repositories by clicking the "×" next to their names
+
+<img src="https://promptless-customer-doc-assets.s3.amazonaws.com/docs-images/org_2lvkgU9erOFxYhtEVVC0ymPrPdF/bc05f421-e940-4f84-b442-6f9181a0eab3-github-app-repository-management.png" alt="GitHub App Repository Management" style={{width:"800px", display: "block", margin: "0 auto", boxShadow: "0 4px 8px rgba(0, 0, 0, 0.1)", marginBottom: "20px"}} />
+
+5. Click "Save" to apply your changes
+
+After updating repository access, the new repositories will be available when creating or editing projects in Promptless. Note that it may take a few minutes for the changes to be reflected in the Promptless dashboard. If you don't see newly added repositories immediately, you may need to click the "refresh repos" icon in the integrations page to update the repository list.
 
 ## Project Setup and Permissions
 
@@ -50,4 +67,4 @@ When trigger directories are specified, only PRs that contain changes to those d
 
 Promptless uses the official [Github App specification](https://docs.github.com/en/apps/creating-github-apps/about-creating-github-apps) to authenticate with Github. Promptless authenticates securely with JWTs generated by the Github App installation. 
 
-This ensures that Promptless has read and write access to the repositories that you select, and that either you or Promptless can revoke access at any time. 
+This ensures that Promptless has read and write access to the repositories that you select, and that either you or Promptless can revoke access at any time.