feat(xanthous): Add an auto-rest command

Add a command that automatically rests (essentially just stepping the
game forwards) until the character's hitpoints are back to full.

Currently due to the time it takes for the character to heal this takes
a bit too long - my thought there is to make the per-step delay for
autocommands different depending on the specific autocommand.

Change-Id: I40378c29d3d9d19e9787af1f015bde65fd08868c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3221
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI

users/grfn/xanthous/src/Xanthous/App.hs

@@ -330,6 +330,8 @@ handleCommand (StartAutoMove dir) = do
   runAutocommand $ AutoMove dir
   continue
 
+handleCommand Rest = runAutocommand AutoRest >> continue
+
 --
 
 handleCommand ToggleRevealAll = do