settings: Add scroll for settings page

This commit replaced Column with
ListView Widget to enable scrolling effect.

Author: MritunjayTiwari14

lib/widgets/settings.dart

@@ -20,7 +20,7 @@ class SettingsPage extends StatelessWidget {
     return Scaffold(
       appBar: ZulipAppBar(
         title: Text(zulipLocalizations.settingsPageTitle)),
-      body: Column(children: [
+      body: ListView(children: [
         const _ThemeSetting(),
         const _BrowserPreferenceSetting(),
         const _VisitFirstUnreadSetting(),

test/widgets/settings_test.dart

@@ -160,6 +160,24 @@ void main() {
     }, variant: TargetPlatformVariant({TargetPlatform.android, TargetPlatform.iOS}));
   });
 
+  group('SettingPageScrollBehavior', () {
+    testWidgets('scroll settings list when screen size is small', (tester) async {
+      tester.view.physicalSize = const Size(200, 200);
+      tester.view.devicePixelRatio = 1.0;
+      addTearDown(tester.view.reset);
+      await prepare(tester);
+
+      final lastElementFinder = GlobalSettingsStore.experimentalFeatureFlags.isNotEmpty
+          ? find.text("Experimental features")
+          : find.text("Mark messages as read on scroll");
+      check(lastElementFinder.evaluate().isEmpty).equals(true);
+
+      await tester.scrollUntilVisible(lastElementFinder, 100,
+        scrollable: find.byType(Scrollable));
+      check(lastElementFinder.evaluate().isEmpty).equals(false);
+    });
+  });
+
   group('VisitFirstUnreadSetting', () {
     String settingTitle(VisitFirstUnreadSetting setting) => switch (setting) {
       VisitFirstUnreadSetting.always => 'First unread message',