feat: Add navigation and data entry page

lib/navigator/view.dart

@@ -0,0 +1,44 @@
+import 'package:flutter/material.dart';
+import 'package:migrainetracker/data_entry/view.dart';
+
+class NavigatorPage extends StatefulWidget {
+  const NavigatorPage({Key? key}) : super(key: key);
+
+  @override
+  State<NavigatorPage> createState() => _NavigatorPageState();
+}
+
+class _NavigatorPageState extends State<NavigatorPage> {
+  int currentPageIndex = 0;
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: const Text("Migraine Tracker"),
+      ),
+      bottomNavigationBar: NavigationBar(
+        destinations: const <Widget>[
+          NavigationDestination(
+            icon: Icon(Icons.explore),
+            label: 'Today',
+          ),
+          NavigationDestination(
+            icon: Icon(Icons.commute),
+            label: 'Stats',
+          ),
+        ],
+        selectedIndex: currentPageIndex,
+        onDestinationSelected: (int index) {
+          setState(() {
+            currentPageIndex = index;
+          });
+        },
+      ),
+      body: <Widget>[
+        const DataEntryPage(),
+        const Placeholder(),
+      ][currentPageIndex],
+    );
+  }
+}