Improve error message for 3D model download when 3D viewer is not open (

#574)

* fix error msg

* format code

* improve msg

src/lib/download-fns/download-gltf.ts

@@ -13,7 +13,7 @@ export const downloadGltf = async (
 
   if (!threeJsObject) {
     throw new Error(
-      "No 3D object found, run the snippet before downloading the 3d model",
+      "To download the 3D model, please open the 3D view first and run the snippet",
     )
   }