feat: main framework complete.

app/lib/constants/sp_keys.dart

@@ -1,3 +1,4 @@
 class SPKeys {
   static final String brightnessMode = 'BRIGHTNESS_MODE';
+  static final String userLanguage = 'USER_LANGUAGE';
 }

app/lib/constants/supported_locales.dart

@@ -0,0 +1,22 @@
+import 'package:flutter/material.dart';
+
+enum SupportedLocale {
+  zh_CN,
+  en,
+}
+
+const zh_CN = Locale('zh', 'CN');
+const en = Locale('en');
+
+const supportedLocales = [
+  zh_CN,
+  en,
+];
+
+const supportedLocaleNames = {
+  SupportedLocale.zh_CN: '简体中文',
+  SupportedLocale.en: 'English',
+};
+
+Locale getSupportedLocale(SupportedLocale supportedLocale) => supportedLocales[supportedLocale.index];
+