Make chessboard fit its window.

lib/chessapp/chess_app.dart

@@ -26,11 +26,11 @@ class ChessApp extends StatelessWidget {
             ),
           ),
           child: Center(
+            child: FittedBox(
+              fit: BoxFit.contain,
               child: Column(
                 children: [
-              FittedBox(
+                  Container(
-                fit: BoxFit.contain,
-                child: Container(
                     margin: const EdgeInsets.all(20),
                     child: BlocProvider(
                       create: (_) => ChessBloc.getInstance(),
@@ -43,7 +43,6 @@ class ChessApp extends StatelessWidget {
                       ),
                     ),
                   ),
-              ),
                   StreamBuilder(
                     stream: ServerConnection.getInstance().channel.stream,
                     builder: (context, snapshot) {
@@ -53,7 +52,9 @@ class ChessApp extends StatelessWidget {
                     },
                   )
                 ],
-          )),
+              ),
+            ),
+          ),
         ),
       ),
     );