Added Desktop View

ac_web/lib/Layouts/MainApp.dart

@@ -1,5 +1,6 @@
 import 'package:flutter/material.dart';
 
+import 'DesktopView.dart';
 import 'MobileView.dart';
 
 class MainApp extends StatelessWidget {
@@ -31,7 +32,16 @@ class MainApp extends StatelessWidget {
           brightness: Brightness.dark,
         )
       ),
-      home: const MobileView(),
+      // Wide windows show all three pages next to each other, narrow ones
+      // switch between them through the navigation bar.
+      home: LayoutBuilder(
+        builder: (context, constraints) {
+          if (constraints.maxWidth >= DesktopView.minimumWidth) {
+            return const DesktopView();
+          }
+          return const MobileView();
+        },
+      ),
     );
   }
 }