Serving other MIME types

[sigilante]

I modified /lib/schooner.hoon to serve other types for a tutorial.

E.g.

+$  resource
  $%  
    [%manx m=manx]            [%json j=json]
    [%html h=cord]            [%login-redirect l=cord]
    [%redirect o=cord]        [%plain p=tape]
    [%none ~]                 [%stock ~]
    [%image-png p=@]          [%audio-wav p=@]
  ==

and

    ::
      %image-png
    :_  `(as-octs:mimes:html p.resource)
    :-  http-status
    (weld headers ['content-type'^'image/png']~)
    ::
      %audio-wav
    :_  `(as-octs:mimes:html p.resource)
    :-  http-status
    (weld headers ['content-type'^'audio/wav']~)

Honestly it would probably be nicer to build these automatically as a gate rather than hardcode n of them. What do you think?

Alternatively I can just PR the changes.