新增 设置 - 显示通知重要程度

此功能为 AOSP 通知的标准功能，从 MIUI 12 开始被隐藏
请参见：
- https://developer.android.com/guide/topics/ui/notifiers/notifications?hl=zh-cn#importance
- https://www.coolapk.com/feed/24638207?shareKey=YzcwZGMzNzM2NWQ3NjIyOTU4NzY~

app/src/main/res/values/arrays.xml

@@ -8,5 +8,6 @@
         <item>com.miui.home</item>
         <item>com.miui.mediaeditor</item>
         <item>com.android.updater</item>
+        <item>com.android.settings</item>
     </string-array>
 </resources>

app/src/main/res/values/strings.xml

@@ -144,4 +144,7 @@
     <string name="updater">Updater</string>
     <string name="remove_ota_validate">*Remove OTA validate [LAB]</string>
     <string name="remove_ota_validate_summary">- Only support VAB series use, please do not open other series.\n- No need for internal testing qualification to flash into the full internal testing package.\n- Those who have internal testing permission will not be able to receive internal testing updates, and can be used to block system updates.\n- After cross-version type upgrade, it is recommended to clear data.\n- Unofficial ROM usage is not supported.</string>
+    <string name="settings">Settings</string>
+    <string name="show_notification_importance">Show notification importance</string>
+    <string name="show_notification_importance_summary">Show notification importance settings which are hidden in MIUI 12 and later versions</string>
 </resources>