Added .mov and .mp4 to authorised extensions for uploads

Hi all

I’ve added support for .mov and .mp4 as authorised extensions for uploads.
Due to server limitations I’ve chosen to limit file size to 16MB which should be ok for short videos to show specific issues.

If you don’t think that’s enough let me know privately but I wish to avoid large uploads as server space can become expensive if not kept tightly controlled.

Thanks