refactor: 标准化

src/onebot11/event/notice/OB11GroupEssenceEvent.ts

@@ -1,7 +1,8 @@
 import { OB11GroupNoticeEvent } from './OB11GroupNoticeEvent';
 export class OB11GroupEssenceEvent extends OB11GroupNoticeEvent {
-    notice_type = 'group_essence';
+    notice_type = 'essence';
     message_id: number;
+    sub_type: 'add' | 'delete' = "add";
 
     constructor(groupId: number, message_id: number) {
         super();