Restructure index.js, simplify translation process

No big change

module/webui/locales/A-template.json

@@ -1,4 +1,5 @@
 {
+    "language": "English",
     "header": {
         "title": "Tricky Addon - Update Target List"
     },

module/webui/locales/A-translate.md

@@ -15,17 +15,4 @@
 2. Make a copy of `/module/webroot/locales/A-template.json`
 3. Rename it to `language_code-COUNTRY_CODE.json`, e.g., `en-US.json`.
 4. Translate the string value inside.
-5. Add `langauge-option` into `/module/webroot/index.html`.
-
-Format:
-```xml
-<button class="language-option" data-lang="language_code-COUNTRY_CODE">languageName</button>
-```
-
-Example:
-```xml
-<div class="language-menu">
-    <button class="language-option" data-lang="en-US">English</button>
-</div>
-```
-Finally, Create a Pull Request.
+6. Create a Pull Request.

module/webui/locales/en-US.json

@@ -1,4 +1,5 @@
 {
+    "language": "English",
     "header": {
         "title": "Tricky Addon - Update Target List"
     },

module/webui/locales/es-ES.json

@@ -1,4 +1,5 @@
 {
+    "language": "Español",
     "header": {
         "title": "Tricky Addon - Update Target List"
     },

module/webui/locales/ja-JP.json

@@ -1,4 +1,5 @@
 {
+    "language": "日本語",
     "header": {
         "title": "Tricky Addon - Update Target List"
     },

module/webui/locales/ru-RU.json

@@ -1,4 +1,5 @@
 {
+    "language": "Русский",
     "header": {
         "title": "Tricky Addon - Обновить список целей"
     },

module/webui/locales/tl-PH.json

@@ -1,4 +1,5 @@
 {
+    "language": "Tagalog",
     "header": {
         "title": "Tricky Addon - I-update ang Target List"
     },

module/webui/locales/zh-CN.json

@@ -1,4 +1,5 @@
 {
+    "language": "中文（简体）",
     "header": {
         "title": "TS插件 - 更新目标列表"
     },

module/webui/locales/zh-TW.json

@@ -1,4 +1,5 @@
 {
+    "language": "中文（繁体）",
     "header": {
         "title": "TS插件 - 更新目標列表"
     },