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>

.gitignore

@@ -0,0 +1,13 @@
+# Developer tools' files
+.lite_workspace.lua
+
+# Neutralinojs binaries and builds
+/bin
+/dist
+
+# Neutralinojs client (minified)
+neutralino.js
+
+# Neutralinojs related files
+.storage
+*.log