Added tag (#223)

Now that there is a new tag "3D", Scene3D should definitely have it as well.

Author: HalfstarDev

assets/scene3d.json

@@ -19,6 +19,7 @@
   "project_url": "https://github.com/indiesoftby/defold-scene3d",
   "stars": 145,
   "tags": [
+    "3d",
     "Art assets",
     "Camera",
     "Shaders",
@@ -27,4 +28,4 @@
   ],
   "timestamp": 1644886794.0,
   "website_url": ""
-}
+}