README: show Rudder running as a desktop app

Output 3 showed only the map app as a desktop app. Rudder is the desktop
example the README describes, and it has now been built with
`bun run desktop:build rudder-voice` and run on Linux: a screenshot of the
running app goes under the map app's, with one line on how to build it.

The PNG carries no text chunks (the original recorded its creation time
and timezone); the pixels are unchanged.

README.md

@@ -495,6 +495,11 @@ bun run phone          # builds the app and installs it on a phone or emulator
 
 ![Desktop app (Tauri) — proven, not yet in production](documentation/readme-images/deploy5-desktop.png)
 
+**Rudder, the voice-to-text plugin, runs as its own desktop app too**, built with
+`bun run desktop:build rudder-voice` ([HOWTO-build-the-desktop-app](./documentation/HOWTO-build-the-desktop-app.md)).
+
+![Rudder as a desktop app on Linux: offline voice-to-text](documentation/readme-images/deploy5-desktop-rudder.png)
+
 <details>
 <summary><b>More about the desktop app</b></summary>