ajustes de layout

lib/main.dart

@@ -31,6 +31,13 @@ class MyApp extends StatelessWidget {
     return MaterialApp(
       debugShowCheckedModeBanner: false,
       title: 'CONTROLE DE ACESSO',
+      theme: ThemeData(
+        scrollbarTheme: ScrollbarThemeData(
+          thickness: MaterialStateProperty.all<double>(15),
+          thumbVisibility: MaterialStateProperty.all<bool>(true),
+          thumbColor: MaterialStateProperty.all<Color>(Colors.black38),
+        )
+      ),
       onUnknownRoute: (RouteSettings settings) {
         return MaterialPageRoute(
           builder: (context) => Scaffold(