refactor: convert to ECMAScript where necessary

Also drop @league-of-foundry-developers/foundry-vtt-types.

src/apps/actor/creature-sheet.ts

@@ -1,16 +0,0 @@
-// SPDX-FileCopyrightText: 2021 Johannes Loher
-//
-// SPDX-License-Identifier: MIT
-
-import { DS4ActorSheet } from "./base-sheet";
-
-/**
- * The Sheet class for DS4 Creature Actors
- */
-export class DS4CreatureActorSheet extends DS4ActorSheet {
-    static override get defaultOptions(): ActorSheet.Options {
-        return foundry.utils.mergeObject(super.defaultOptions, {
-            classes: ["sheet", "ds4-actor-sheet", "ds4-creature-sheet"],
-        });
-    }
-}