feat(xan): Generate random villages

This algorithm is a little rough around the edges right now, but
generally the idea is we find a relatively closed-off region of the map,
and place rooms randomly on it, expanding them until they run into each
other, then we put doors in the walls of the rooms and a single door
opening into the region. Later on, we'll generate friendly (or
unfriendly!) NPCs to put in those rooms.

Change-Id: Ic989b9905f55ad92a01fdf6db11aa57afb4ce383
Reviewed-on: https://cl.tvl.fyi/c/depot/+/726
Reviewed-by: glittershark <grfn@gws.fyi>

users/glittershark/xanthous/package.yaml

@@ -54,6 +54,7 @@ dependencies:
 - MonadRandom
 - mtl
 - optparse-applicative
+- parallel
 - parser-combinators
 - pointed
 - random
@@ -67,6 +68,7 @@ dependencies:
 - stache
 - semigroupoids
 - tomland
+- transformers
 - text
 - text-zipper
 - vector