link-server-hook: add tile serving, %png mounts
link-server-hook: add tile serving, %png mounts

Front-end work necessitates images being mounted, and the tile served on
Landscape. This commit adds it to link-server-hook.

urbit/urbit,ngzax/urbit,jfranklin9000/urbit,ngzax/urbit,urbit/urbit,jfranklin9000/urbit,urbit/urbit,ngzax/urbit,jfranklin9000/urbit,jfranklin9000/urbit,jfranklin9000/urbit,ngzax/urbit,urbit/urbit,jfranklin9000/urbit,jfranklin9000/urbit,ngzax/urbit,urbit/urbit,urbit/urbit,ngzax/urbit,ngzax/urbit,urbit/urbit