Use IIFE for entry points

ext/bg/js/background-main.js

@@ -19,9 +19,7 @@
  * Backend
  */
 
-async function main() {
+(async () => {
     window.yomichanBackend = new Backend();
     await window.yomichanBackend.prepare();
-}
-
-main();
+})();

ext/bg/js/context-main.js

@@ -88,8 +88,6 @@ async function mainInner() {
     });
 }
 
-async function main() {
+(async () => {
     window.addEventListener('DOMContentLoaded', mainInner, false);
-}
-
-main();
+})();

ext/bg/js/search-main.js

@@ -52,7 +52,7 @@ function injectSearchFrontend() {
     }
 }
 
-async function main() {
+(async () => {
     await yomichan.prepare();
 
     const displaySearch = new DisplaySearch();
@@ -78,6 +78,4 @@ async function main() {
     yomichan.on('optionsUpdated', applyOptions);
 
     await applyOptions();
-}
-
-main();
+})();

ext/bg/js/settings/popup-preview-frame-main.js

@@ -19,9 +19,7 @@
  * SettingsPopupPreview
  */
 
-async function main() {
+(async () => {
     const instance = new SettingsPopupPreview();
     await instance.prepare();
-}
-
-main();
+})();

ext/fg/js/content-script-main.js

@@ -61,7 +61,7 @@ async function createPopupProxy(depth, id, parentFrameId, url) {
     return popup;
 }
 
-async function contentScriptMain() {
+(async () => {
     await yomichan.prepare();
 
     const data = window.frontendInitializationData || {};
@@ -128,6 +128,4 @@ async function contentScriptMain() {
     window.addEventListener('fullscreenchange', applyOptions, false);
 
     await applyOptions();
-}
-
-contentScriptMain();
+})();

ext/fg/js/float-main.js

@@ -67,8 +67,6 @@ async function popupNestedInitialize(id, depth, parentFrameId, url) {
     await applyOptions();
 }
 
-async function main() {
+(async () => {
     new DisplayFloat();
-}
-
-main();
+})();