Book cover image doesn't allow upload of some file types
Expected behaviour
User should be able to upload from the UI to Metadata modal of the book, cover images with the formats: TIFF, EPS, PNG, JPEG and PSD, as documented here.
cc: @DioneMentis it should allow as well .TIF as we had covers with this extensions in testing files.
Current behaviour
We can only upload cover images with file types .jpeg, .jpg, .png, .gif.
Steps to reproduce
Try to upload cover image in Metadata modal with file type tiff, tif, eps or psd.