Support additional mimetypes for text-based file attachments.
Review Request #114 — Created Dec. 2, 2022 and updated
This adds support for various alternative JSON mimetypes and YAML mimetypes, ensuring that thumbnails display content correctly and that they can be reviewed as text files when using an `application/` mimetype. The text-based review UI uses the text-based mimetype as the basis for the list of supported mimetypes, so these won't get out of sync. Testing Done: Unit tests pass. Manually tested with the new mimetypes, ensuring that thumbnails and reviews worked correctly. Verified the fix with a customer. Reviewed at https://reviews.reviewboard.org/r/12730/