Update example game some, update engine some

* Add RevealAction/UnrevealAction for revealing/hiding items in a room
* Add a lot of checks for items being revealed when it's attempted to be
  triggered
* Implement TeleportAction (mostly)
* For all Check* family of actions, the `yes` and `no` values may be
  just be a single action instead of an array of actions
* Change up how room descriptions and stuff work, mostly so that you can
  specify multiple lines in an array so you can preserve paragraph
  breaks when displayed.
* Example game has some more content

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

agame/room.py

@@ -11,14 +11,14 @@ __all__ = ("Room",)
 class Room:
     id: str
     name: str
-    desc: str
+    desc: Union[str, Sequence[str]]
     items: MutableMapping[str, ItemInst]
 
     def __init__(
         self,
         id: str,
         name: str,
-        desc: str,
+        desc: Union[str, Sequence[str]],
         items: Union[Sequence[ItemInst], MutableMapping[str, ItemInst]],
     ):
         self.id = id