Add input file types to sandbox upload button

Please, add types to this button:

After click this button I open the Downloads folder and trying to find target glb/gltf file. It is pretty hard to find needed file in this trash :smiley:

But it is much more convenient, when input has the target filter:
<input type="file" id="files" multiple="" accept=".glb,.gltf,.obj,.babylon">

Do you want to make a PR for it ?

Check this out =)