群解散时，无论在群组中的哪个页面，都退回到会话列表页面

pages/im/group/announceCreate.vue

@@ -16,8 +16,12 @@
         createGroupAnnouncement,
         getGroupAnnouncement
     } from '@/apis/interfaces/im.js'
+    import onGroupDismiss from '@/utils/im/onGroupDismiss.js'
 
     export default {
+        mixins: [
+            onGroupDismiss
+        ],
         data() {
             return {
                 targetId: '',