Enhancement request: support HEIC files

This should be an easy thing to add, and would add some convenience. When I try uploading a HEIC file to attach to a Message for eventual use with gpt-4-vision, I get this error:

2022-11-10 18-15.heic: Error code: 400 - {'error': {'message': "Invalid file format. Supported formats: ['c', 'cpp', 'csv', 'docx', 'html', 'java', 'json', 'md', 'pdf', 'php', 'pptx', 'py', 'rb', 'tex', 'txt', 'css', 'jpeg', 'jpg', 'js', 'gif', 'png', 'tar', 'ts', 'xlsx', 'xml', 'zip']", 'type': 'invalid_request_error', 'param': None, 'code': None}}

So my request is to support heic files, since it can be the native file format stored on iPhones, and when I dragged a photo sent from a family member via Messages to a folder on disk, it was this format.

I’ll add code in my chatbot to convert to jpeg for now, but it would be cleaner if the API supported it, even if it simply converts it to jpeg.