nav: Add an About Zulip button to the main menu

Fixes: zulip#1128

Author: tomlin7

lib/widgets/home.dart

@@ -4,6 +4,7 @@ import 'package:flutter/material.dart';
 
 import '../generated/l10n/zulip_localizations.dart';
 import '../model/narrow.dart';
+import 'about_zulip.dart';
 import 'action_sheet.dart';
 import 'app.dart';
 import 'app_bar.dart';
@@ -269,6 +270,7 @@ void _showMainMenu(BuildContext context, {
     // TODO(#97): Settings
     // TODO(#661): Notifications
     // const SizedBox(height: 8),
+    const _AboutZulipButton(),
     // TODO(#1095): VersionInfo
   ];
 
@@ -556,6 +558,23 @@ class _SwitchAccountButton extends _MenuButton {
   }
 }
 
+class _AboutZulipButton extends _MenuButton {
+  const _AboutZulipButton();
+
+  @override
+  IconData get icon => ZulipIcons.info;
+
+  @override
+  String label(ZulipLocalizations zulipLocalizations) {
+    return zulipLocalizations.aboutPageTitle;
+  }
+
+  @override
+  void onPressed(BuildContext context) {
+    Navigator.of(context).push(AboutZulipPage.buildRoute(context));
+  }
+}
+
 /// Apply [Transform.scale] to the child widget when tapped, and reset its scale
 /// when released, while animating the transitions.
 class AnimatedScaleOnTap extends StatefulWidget {

test/widgets/home_test.dart

@@ -5,6 +5,7 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:zulip/api/model/events.dart';
 import 'package:zulip/model/narrow.dart';
 import 'package:zulip/model/store.dart';
+import 'package:zulip/widgets/about_zulip.dart';
 import 'package:zulip/widgets/app.dart';
 import 'package:zulip/widgets/app_bar.dart';
 import 'package:zulip/widgets/home.dart';
@@ -238,6 +239,16 @@ void main () {
       check(find.byType(ProfilePage)).findsOne();
       check(find.text(eg.selfUser.fullName)).findsAny();
     });
+
+    testWidgets('_AboutZulipButton', (tester) async {
+      await prepare(tester);
+      await tapOpenMenu(tester);
+
+      await tester.tap(find.byIcon(ZulipIcons.info));
+      await tester.pump(Duration.zero); // tap the button
+      await tester.pump(const Duration(milliseconds: 250)); // wait for animation
+      check(find.byType(AboutZulipPage)).findsOne();
+    });
   });
 
   group('_LoadingPlaceholderPage', () {