Add a test for manually written header tags

Author: ehuss

tests/testsuite/markdown/basic_markdown/expected/html.html

@@ -62,4 +62,8 @@ <h2 id="style"><a class="header" href="#style">Style</a></h2>
 </style>
 <style media="(width &lt; 500px)">
 .bar { background-color: green }
-</style>
+</style>
+<h2 id="manual-headers"><a class="header" href="#manual-headers">Manual headers</a></h2>
+<h2 id="my header"><a class="header" href="#my header"><a href="#foo">My Header</a></a></h2>
+
+<h3 id="another-header"><a class="header" href="#another-header">Another header</a></h3>

tests/testsuite/markdown/basic_markdown/src/html.md

@@ -92,3 +92,9 @@ const x = 'some *text* inside';
 <style media="(width < 500px)">
 .bar { background-color: green }
 </style>
+
+## Manual headers
+
+<h2 id="my header"><a href="#foo">My Header</a></h2>
+
+<h3>Another header</h3>