Add markdown format support (#25)

Co-authored-by: Dawid Dziurla <dawidd0811@gmail.com>

node_modules/showdown/test/features/tables/with-span-elements.html

@@ -0,0 +1,26 @@
+<table>
+    <thead>
+    <tr>
+        <th>First Header</th>
+        <th>Second Header</th>
+    </tr>
+    </thead>
+    <tbody>
+    <tr>
+        <td><strong>bold</strong></td>
+        <td><img src="foo.jpg" alt="img" /></td>
+    </tr>
+    <tr>
+        <td><em>italic</em></td>
+        <td><a href="bla.html">link</a></td>
+    </tr>
+    <tr>
+        <td><code>some code</code></td>
+        <td><a href="www.google.com">google</a></td>
+    </tr>
+    <tr>
+        <td><a href="http://www.foo.com">www.foo.com</a></td>
+        <td>normal</td>
+    </tr>
+    </tbody>
+</table>