This plugin adds a panel to the Settings->Media page, enabling changes to the file types which are permitted to be uploaded to the media library.
Works great for me as described.
Very simple /wp-admin/options-media.php page that allows the editing of mime types.
I needed this to add svg support, with:
(It currently has an issue for me for uploading svg files, giving "Sorry, this file type is not permitted for security reasons." but this used to work and I'm sure this problem will be fixed shortly.)