Add main_webview which is used for testing

lib/main_webview.dart

@@ -0,0 +1,39 @@
+import 'package:flutter/material.dart';
+
+import 'package:gitjournal/widgets/katex_widget.dart';
+
+void main() => runApp(MyApp());
+
+/// This Widget is the main application widget.
+class MyApp extends StatelessWidget {
+  static const String _title = 'Flutter Code Sample';
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      title: _title,
+      home: MyWidget(),
+    );
+  }
+}
+
+class MyWidget extends StatelessWidget {
+  MyWidget({Key key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: const Text('Sample Code'),
+      ),
+      body: Center(
+        child: Column(
+          children: <Widget>[
+            KatexWidget(r"\\pm\\sqrt{a^2 + b^2}"),
+            KatexWidget(r"\\pm\\sqrt{c^2 + d^2}"),
+          ],
+        ),
+      ),
+    );
+  }
+}