Add spinner during OBJ loading

[mfranzon]

Show a loading spinner or text when OBJ models are being loaded in addObjectToScene to improve user experience during loading times

[iamAmer]

Hi! Could you please assign this issue to me? I’d like to work on it.

[iamAmer]

I've opened a PR #46 for this one

[iamAmer]

@mfranzon you can close this one.