Add 🇨🇳 Chinese simplified (#310)

Thanks to omltcat for the translation!

app/javascript/components/SiteSettings/General/GeneralSiteSettingsP.tsx

@@ -162,6 +162,7 @@ const GeneralSiteSettingsP = ({
               <option value="de">🇩🇪 Deutsch</option>
               <option value="fr">🇫🇷 Français</option>
               <option value="es">🇪🇸 Español</option>
+              <option value="zh-CN">🇨🇳 中文</option>
               <option value="ru">🇷🇺 Русский</option>
               <option value="vi">🇻🇳 Tiếng Việt</option>
             </select>

app/javascript/translations/index.js.erb

@@ -3,6 +3,7 @@ import I18n from "i18n-js"
 I18n.translations = <%= I18n::JS.filtered_translations.to_json %>
 I18n.locale = LOCALE
 
+I18n.pluralization["zh-CN"] = function(count) { return ["other"] }
 I18n.pluralization["vi"] = function(count) { return ["other"] }
 
 export default I18n

config/initializers/locale.rb

@@ -1,11 +1,12 @@
 # Configure I18n to look at subfolders too
 I18n.load_path += Dir[Rails.root.join('config', 'locales', '**', '*.yml')]
 
-I18n.available_locales = [:en, :it, :de, :fr, :ru, :es, :vi]
+I18n.available_locales = [:en, :it, :de, :fr, :es, 'zh-CN', :ru, :vi]
 
 I18n.default_locale = :en
 
 # Custom pluralization rules
 # Those must be mirrored in app/javascript/translations/index.js.erb
 I18n::Backend::Simple.include(I18n::Backend::Pluralization)
+I18n.backend.store_translations 'zh-CN', i18n: { plural: { rule: lambda { |n| :other } } } # Chinese simplified
 I18n.backend.store_translations :vi, i18n: { plural: { rule: lambda { |n| :other } } } # Vietnamese