Transcript file type detection/validation #162
Description
Shortly we will have users uploading transcripts to episodes in Feeder. (And eventually, generating them in our system).
Right now, the podcastindex.org spec defines 4 transcript types to support: HTML, JSON, SRT and VTT. All of which will just return a null mimetype through the file-type package (they're just text).
Is there something more we could return from the Inspect task here, so Feeder can validate you uploaded one of those 4?