add non-configurable escape button to input type, to be used as a way to go backwards or exit menu

fcore/core-key.sml

@@ -134,6 +134,7 @@ sig
     , down: key_code
     , jump: key_code
     , attack: key_code
+    , escape: key_code
     }
 
   val keyFromString: string -> key_code option
@@ -275,6 +276,7 @@ struct
     , down: key_code
     , jump: key_code
     , attack: key_code
+    , escape: key_code
     }
 
   fun keyFromString str =

fcore/frame-input-type.sml

@@ -7,5 +7,6 @@ struct
     , downHeld: bool
     , attackHeld: bool
     , jumpHeld: bool
+    , escapeHeld: bool
     }
 end

fcore/level/player/player.sml

@@ -206,7 +206,15 @@ struct
         , ...
         } = player
 
-      val {leftHeld, rightHeld, upHeld, downHeld, attackHeld, jumpHeld} = input
+      val
+        { leftHeld
+        , rightHeld
+        , upHeld
+        , downHeld
+        , attackHeld
+        , jumpHeld
+        , escapeHeld
+        } = input
 
       val xAxis = getXAxis (leftHeld, rightHeld)
       val facing = getFacing (facing, xAxis)

fcore/options/options-type.sml

@@ -0,0 +1,4 @@
+structure OptionsType =
+struct
+  datatype focus = 
+end