Rename UiHandler file to fit conventions

src/ui/egg-hatch-scene-handler.ts

@@ -1,6 +1,6 @@
 import BattleScene, { Button } from "../battle-scene";
 import { Mode } from "./ui";
-import UiHandler from "./uiHandler";
+import UiHandler from "./ui-handler";
 
 export default class EggHatchSceneHandler extends UiHandler {
   public eggHatchContainer: Phaser.GameObjects.Container;