add changelog; see changelog <3

README.md

@@ -4,9 +4,4 @@ cd hs-game
 nix run
 ```
 
-todo
-
-- [x] add proper mouse movement
-- [ ] abstract into `Game` and `Game.Internal` with appropriate exports
-- [ ] refactor for correctness
-- [ ] fix depth clipping; near squares show oft before far
+todo moved to CHANGELOG.md