You can use HTML tables on GitHub (but not on StackOverflow)
<table>
<tr>
<td>One</td>
<td>Two</td>
</tr>
<tr>
<td colspan="2">Three</td>
</tr>
</table>
Becomes
You can use HTML tables on GitHub (but not on StackOverflow)
<table>
<tr>
<td>One</td>
<td>Two</td>
</tr>
<tr>
<td colspan="2">Three</td>
</tr>
</table>
Becomes