This changes the ToAscinema function to take a storage.TempFile instead
of a storage.FS. It was noticed that when this was being used a
storage.FS was being created just prior to calling this just so that it
could then create a temporary file. It seemed to make more sense to just
pass the temporary file in, instead of needing to expand the storage.FS
interface.
This also renames this method to align with the file format that the
returned io.Reader will contain.
Timothy Messier
b4ce802572