feat: implement consumer and Provider.of test things

lib/navigator/view.dart

@@ -13,6 +13,11 @@ class _NavigatorPageState extends State<NavigatorPage> {
 
   @override
   Widget build(BuildContext context) {
+    var pages = <Widget>[
+      const DataEntryPage(),
+      const Placeholder(),
+    ];
+
     return Scaffold(
       appBar: AppBar(
         title: const Text("Migraine Tracker"),
@@ -35,10 +40,7 @@ class _NavigatorPageState extends State<NavigatorPage> {
           });
         },
       ),
-      body: <Widget>[
-        const DataEntryPage(),
-        const Placeholder(),
-      ][currentPageIndex],
+      body: pages[currentPageIndex],
     );
   }
 }