Initial commit: Unity Needle AR Menu project with MenuScene and SampleScene web apps

Add root .gitignore for Unity Library/Temp/Logs, IDE folders, and node_modules.
Include Assets, Needle TypeScript (MenuController, asset picker, WebXR), and project configuration.

Made-with: Cursor

Needle/MenuScene/src/main.ts

@@ -0,0 +1,3 @@
+import("@needle-tools/engine") /* async import of needle engine */;
+import "./enableXR";
+import "./assetPicker";