Add Simplified Chinese as a system language

The installer asks for the language before the keyboard, and
Setup > Language (omarchy language en|zh) switches it later. Under
zh_CN the menu reads its labels from omarchy-menu.zh-cn.jsonc, the
shell from I18nZh.js through I18n.tr, and notifications are worded
by their sender through omarchy-text, which reads the same table.
User text is never translated.

shell/Commons/qmldir

@@ -2,6 +2,7 @@ module qs.Commons
 singleton AudioNodes 1.0 AudioNodes.qml
 singleton Border 1.0 Border.qml
 singleton Color 1.0 Color.qml
+singleton I18n 1.0 I18n.qml
 singleton IpcRegistry 1.0 IpcRegistry.qml
 singleton InputMethodState 1.0 InputMethodState.qml
 singleton Style 1.0 Style.qml