Add a button to show system status bar (#417)

lib/foundation/appdata.dart

@@ -197,6 +197,7 @@ class Settings with ChangeNotifier {
     'showPageNumberInReader': true,
     'showSingleImageOnFirstPage': false,
     'enableDoubleTapToZoom': true,
+    'showSystemStatusBar': false,
   };
 
   operator [](String key) {

lib/pages/reader/reader.dart

@@ -164,7 +164,9 @@ class _ReaderState extends State<Reader>
     }
     mode = ReaderMode.fromKey(appdata.settings['readerMode']);
     history = widget.history;
-    SystemChrome.setEnabledSystemUIMode(SystemUiMode.immersive);
+    if (!appdata.settings['showSystemStatusBar']) {
+      SystemChrome.setEnabledSystemUIMode(SystemUiMode.immersive);
+    }
     if (appdata.settings['enableTurnPageByVolumeKey']) {
       handleVolumeEvent();
     }

lib/pages/reader/scaffold.dart

@@ -107,7 +107,11 @@ class _ReaderScaffoldState extends State<_ReaderScaffold> {
     if (!_isOpen) {
       SystemChrome.setEnabledSystemUIMode(SystemUiMode.edgeToEdge);
     } else {
-      SystemChrome.setEnabledSystemUIMode(SystemUiMode.immersive);
+      if (!appdata.settings['showSystemStatusBar']) {
+        SystemChrome.setEnabledSystemUIMode(SystemUiMode.immersive);
+      } else {
+        SystemChrome.setEnabledSystemUIMode(SystemUiMode.edgeToEdge);
+      }
     }
     setState(() {
       _isOpen = !_isOpen;

lib/pages/settings/reader.dart

@@ -163,6 +163,13 @@ class _ReaderSettingsState extends State<ReaderSettings> {
             widget.onChanged?.call("enableClockAndBatteryInfoInReader");
           },
         ).toSliver(),
+        _SwitchSetting(
+          title: "Show system status bar".tl,
+          settingKey: "showSystemStatusBar",
+          onChanged: () {
+            widget.onChanged?.call("showSystemStatusBar");
+          },
+        ).toSliver(),
         SelectSetting(
           title: "Quick collect image".tl,
           settingKey: "quickCollectImage",