This removes the minimum on width and height, instead it will just used
the largest width, height seen as the initial size for the asciicast.
This also provides the ability to still set a minimum via options to
convert.ToAsciicast if the caller has a known minimum size. Also note
that in cases where there is no size information, ie if there was no pty
request, this will still pick a default size of 80x24.
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
irenarindos