[Panlingual] Add a description for per app language.

- This is to notify some app may not support to user.

Bug: 228415129
Test: local
Change-Id: I6205e0b5fdb3ee42a22ae4995c99e9d8dc5e0a2d

res/xml/app_locale_details.xml

@@ -19,14 +19,20 @@
     xmlns:settings="http://schemas.android.com/apk/res-auto"
     android:title="@string/app_locale_picker_title">
 
+    <com.android.settingslib.widget.TopIntroPreference
+        android:title="@string/desc_app_locale_disclaimer"
+        android:order="1"/>
+
     <com.android.settingslib.widget.BannerMessagePreference
         android:key="key_warnings"
+        android:order="20"
         android:icon="@drawable/ic_error_outline"
         android:title="@string/warnings_title"
         android:summary="@string/warnings_summary"/>
 
     <com.android.settingslib.widget.LayoutPreference
         android:key="app_locale_description"
+        android:order="30"
         android:layout="@layout/app_locale_details_description"
         android:selectable="false"
         android:visibility="gone"