QAG-63: (docs) Add settings.php customization instructions

Refs: README.md

Author: tormi

README.md

@@ -20,6 +20,9 @@ This project is a tailored fork of the popular [drupal-composer template](https:
      - For DDEV: Update project settings in `.ddev/config.yaml`
      - For Lando: Update project settings in `.lando.yml`
    - Update project name in `scripts/syncdb.sh` for database synchronization
+   - Adjust `web/sites/default/settings.php` for environment-specific configurations:
+     - Update Config Split settings for different environments (production, main, local)
+     - Configure Stage File Proxy origin URL
 
 3. **Set up CircleCI**
    - Log in to [CircleCI](https://app.circleci.com/) using your GitHub account.