update readme with overlay

Author: antheas

docs/overlay.gif

@@ -46,9 +46,12 @@ overlay, web app for it ([hhd.dev](https://hhd.dev)) that also works locally wit
 - UI based Configuration
   - Generic API that can be used from bash scripts (through `curl`)
   - Decky Plugin
-  - Webapp on https://hhd.dev and through Electron.
+  - Gamemode Overlay, web app, and desktop app
 - Built-in updater.
 
+## Showcase
+![Overlay](./docs/overlay.gif)
+
 ## <a name="devices"></a>Supported Devices
 The following devices have been verified to work correctly, with QAM, 
 Paddles/extra buttons, RGB remapping, Touchpad, and Gyro support.