app-catalog: Improve the README for app-catalog

Signed-off-by: Vincent T <vtaylor@microsoft.com>

app-catalog/README.md

@@ -2,3 +2,52 @@
 
 This plugin adds an app catalog to Headlamp, powered by ArtifactHub and Helm.
 
+![Screenshot of the Headlamp UI with the App Catalog browse page](https://github.com/user-attachments/assets/eeee154a-9146-4132-9bb8-a9e57d863161 "Headlamp UI with App Catalog browse page")
+
+## About the App Catalog
+
+This plugin enables the ability to install Helm charts from artifacthub directly within Headlamp. 
+
+*Note: By default, the App Catalog plugin has its filter set to "Official". This can be changed by navigating to the settings page using the `Settings` button to the right of the title bar.*
+
+## Developing Headlamp Plugins
+
+### Setting up the Environment
+
+1. Run the Headlamp app from the main branch:
+
+   - In a terminal window use:
+
+   ```bash
+   cd headlamp-k8s/headlamp/app
+   npm install
+   npm start
+   ```
+
+2. Set up the App Catalog:
+
+   - In a new terminal window, use:
+
+   ```bash
+   cd headlamp-k8s/plugins/app-catalog
+   npm install
+   npm start
+   ```
+
+3. Ensure the App Catalog is enabled
+
+   - From within Headlamp, navigate to the `Settings` page via the sidebar or the gear icon in the top right corner.
+   - Select the `Plugins` tab located in the sidebar.
+   - Enable the App Catalog plugin by toggling the switch to the right of the menu.
+   - Navigate back to the main page of your cluster.
+
+
+
+After completing these steps, you'll see the App Catalog link in the sidebar.
+
+![Screenshot of the App Catalog link in the sidebar](https://github.com/user-attachments/assets/5ee65579-abfc-4820-bf83-bcc4e2bea0f5 "Screenshot of the App Catalog link in the sidebar")
+
+
+## Contributing
+
+We welcome contributions! If you have ideas for improvements or encounter any issues, please open an issue or submit a pull request on our [GitHub repository](https://github.com/headlamp-k8s/plugins).