refactor: use arrow functions for frontend initializers

Author: DavideIadeluca

extensions/mentions/js/src/admin/index.js

@@ -1,6 +1,6 @@
 import app from 'flarum/admin/app';
 
-app.initializers.add('flarum-mentions', function () {
+app.initializers.add('flarum-mentions', () => {
   app.extensionData
     .for('flarum-mentions')
     .registerSetting({

extensions/mentions/js/src/forum/index.js

@@ -17,7 +17,7 @@ app.mentionFormats = new MentionFormats();
 
 export { default as extend } from './extend';
 
-app.initializers.add('flarum-mentions', function () {
+app.initializers.add('flarum-mentions', () => {
   // For every mention of a post inside a post's content, set up a hover handler
   // that shows a preview of the mentioned post.
   addPostMentionPreviews();

extensions/subscriptions/js/src/forum/index.js

@@ -8,7 +8,7 @@ import addSubscriptionSettings from './addSubscriptionSettings';
 
 export { default as extend } from './extend';
 
-app.initializers.add('flarum-subscriptions', function () {
+app.initializers.add('flarum-subscriptions', () => {
   addSubscriptionBadge();
   addSubscriptionControls();
   addSubscriptionFilter();

extensions/tags/js/src/forum/index.ts

@@ -10,7 +10,7 @@ import addTagComposer from './addTagComposer';
 
 export { default as extend } from './extend';
 
-app.initializers.add('flarum-tags', function () {
+app.initializers.add('flarum-tags', () => {
   app.tagList = new TagListState();
 
   addTagList();