Add a test for the markdown bug

This way it is easier to know when it has been fixed.

test/markdown_bug_test.dart

@@ -0,0 +1,55 @@
+/*
+  MIT License
+
+  Copyright (c) 2020  Vishesh Handa <me@vhanda.in>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files (the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions:
+
+  The above copyright notice and this permission notice shall be included in all
+  copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+*/
+
+import 'package:gitjournal/core/link.dart';
+import 'package:test/test.dart';
+
+import 'package:markdown/markdown.dart' as md;
+import 'package:flutter_markdown/flutter_markdown.dart';
+
+void main() {
+  //
+  // https://github.com/dart-lang/markdown/issues/293
+  //
+  test('Should parse both', () async {
+    var body = "[[GitJournal]] should match.\n- [ ] task item";
+    var lines = body.split('\n');
+
+    var doc = md.Document(
+      encodeHtml: false,
+      extensionSet: md.ExtensionSet.gitHubFlavored,
+      inlineSyntaxes: [WikiLinkSyntax(), TaskListSyntax()],
+    );
+    var nodes = doc.parseLines(lines);
+    var html = md.renderToHtml(nodes);
+
+    var expectedHtml =
+        """<p><a type="wiki" href="[[GitJournal]]" term="GitJournal">GitJournal</a> should match.</p>
+<ul>
+<li><input type="checkbox" disabled="true" checked="false"></input>task item</li>
+</ul>""";
+
+    expect(html, expectedHtml);
+  });
+}