chore: 删除不再使用的 TypeScript 声明文件，并添加新的插件声明文件

docs/assets/ts/artplayer-plugin-chapter.d.ts

@@ -0,0 +1,21 @@
+import type Artplayer from 'artplayer';
+
+export = artplayerPluginChapter;
+export as namespace artplayerPluginChapter;
+
+type Chapters = {
+    start: number;
+    end: number;
+    title: string;
+}[];
+
+type Option = {
+    chapters?: Chapters;
+};
+
+type Result = {
+    name: 'artplayerPluginChapter';
+    update: (option: Option) => void;
+};
+
+declare const artplayerPluginChapter: (option: Option) => (art: Artplayer) => Result;