Check file type for compatibility with whisper before upload #86
Description
Currently one can upload any file, even stupid ones like pdfs or similar. They only error out ones the runner fails to process them. Checking the file type early in frontend would mean a much better UX because the user learns about the mistake before even submitting the job. It would also be more efficient since the backend doesn't have to store these jobs in the database and the runner doesn't have to start to process them.