add switch for theme toggle

lib/app.dart

@@ -16,7 +16,7 @@ final lightThemeData = ThemeData(
   hintColor: Colors.grey,
   iconTheme: IconThemeData(color: Colors.black),
   primaryIconTheme: IconThemeData(color: Colors.red, opacity: 1.0, size: 50.0),
-  colorScheme: ColorScheme.light(primary: Colors.blue),
+  colorScheme: ColorScheme.light(primary: Colors.black),
   accentColor: Color.fromRGBO(45, 194, 98, 0.2),
   buttonColor: Color.fromRGBO(45, 194, 98, 1.0),
   buttonTheme: ButtonThemeData().copyWith(

lib/ui/settings/theme_switch_widget.dart

@@ -0,0 +1,21 @@
+import 'package:flutter/material.dart';
+import 'package:flutter/widgets.dart';
+
+class ThemeSwitchWidget extends StatelessWidget {
+  const ThemeSwitchWidget({Key key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return Switch(
+      value: true,
+      activeColor: Colors.black,
+      onChanged: (bool value) {
+        print(value);
+      },
+      activeThumbImage: new NetworkImage(
+          'https://cdn0.iconfinder.com/data/icons/multimedia-solid-30px/30/moon_dark_mode_night-512.png'),
+      inactiveThumbImage: new NetworkImage(
+          'https://cdn0.iconfinder.com/data/icons/multimedia-solid-30px/30/moon_dark_mode_night-512.png'),
+    );
+  }
+}

lib/ui/settings_page.dart

@@ -12,6 +12,7 @@ import 'package:photos/ui/settings/info_section_widget.dart';
 import 'package:photos/ui/settings/security_section_widget.dart';
 import 'package:photos/ui/settings/social_section_widget.dart';
 import 'package:photos/ui/settings/support_section_widget.dart';
+import 'package:photos/ui/settings/theme_switch_widget.dart';
 
 class SettingsPage extends StatelessWidget {
   const SettingsPage({Key key}) : super(key: key);
@@ -26,6 +27,10 @@ class SettingsPage extends StatelessWidget {
   Widget _getBody(BuildContext context) {
     final hasLoggedIn = Configuration.instance.getToken() != null;
     final List<Widget> contents = [];
+    contents.add(Row(
+        mainAxisAlignment: MainAxisAlignment.spaceAround,
+        crossAxisAlignment: CrossAxisAlignment.center,
+        children: const [ThemeSwitchWidget()]));
     final sectionDivider = Divider(
       height: 10,
       color: Theme.of(context).colorScheme.onSurface.withOpacity(0.4),