Add Traditional Chinese, Hong Kong translation (zh-HK) (#1544)

* Added Chinese Traditional Hong Kong (zh-HK) for Ruby

* Added translations for Ruby.

* Added Chinese Traditional Hong Kong (zh-HK) for JS

* Added translations for javascript code.

* Rearrange language references in mastodon.jsx

* Break `addLocaleData` into multiple lines. Make future commit more readable.
* Roughly re-sort the languages in alphabetical orders
  (only manually put English on top because it is default).

* Sort application.rb locale with alphabetical order

With exception that English (default language) goes first.
Improve code readability.

* Resort language selection box alphabetically

Sort HUMAN_LOCALES in the alphabetical order of display name
(except English, the default language, come first).

Improve usability.

app/helpers/settings_helper.rb

@@ -6,15 +6,15 @@ module SettingsHelper
     de: 'Deutsch',
     es: 'Español',
     eo: 'Esperanto',
-    pt: 'Português',
     fr: 'Français',
     hu: 'Magyar',
-    uk: 'Українська',
-    'zh-CN': '简体中文',
+    pt: 'Português',
     fi: 'Suomi',
     ru: 'Русский',
+    uk: 'Українська',
     ja: '日本語',
-
+    'zh-CN': '简体中文',
+    'zh-HK': '繁體中文（香港）',
   }.freeze
 
   def human_locale(locale)