Initial Neutralino.js POC for kokoro-widget

Lightweight alternative to the Electron build (~5MB vs ~300MB).
Uses system webview (WebKit2GTK on Linux, WKWebView on macOS,
WebView2 on Windows). Same UI and feature set as the Electron build:
WebSocket audio client, volume control, host/port settings, tray icon,
hide-to-tray on close, CLI args (--host, --port, --volume).

Note: Linux requires libwebkit2gtk-4.0 or libwebkit2gtk-4.1.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

README.md

@@ -0,0 +1,6 @@
+# neutralinojs-zero
+An empty Neutralinojs app, extend as you wish
+
+```
+neu create myapp --template neutralinojs/neutralinojs-zero
+```