done adding export-collision functionality, including collision message, in functional core. Next: add imperative shell scaffolding

fcore/common-update.sml

@@ -29,6 +29,18 @@ struct
       (model, [FILE msg])
     end
 
+  fun getCollisionMsg (model: app_type) =
+    let
+      val {squares, canvasWidth, canvasHeight, modalNum, ...} = model
+      val exportString =
+        CollisionTree.toCollisionString (squares, canvasWidth, canvasHeight, modalNum)
+      val msg = EXPORT_COLLISIONS exportString
+
+      val model = AppWith.modalNum (model, 0)
+    in
+      (model, [FILE msg])
+    end
+
   (* unimplemented *)
   fun useSquaresInNormalMode (model, squares) = (model, [])