add Django icon (#341)

Proportions comes from the favicon, the original vector version can be found
in the projects repository:
https://github.com/django/djangoproject.com/tree/master/djangoproject/static/img

README.md

@@ -339,6 +339,7 @@ Say thanks!
 </tr>
 <tr>
 <td>Semaphore CI<br><img src="images/svg/semaphoreci.svg" width="125" title="Semaphore CI" /><br>641 Bytes</td>
+<td>Django Project<br><img src="images/svg/djangoproject.svg" width="125" title="Django Project" /><br>444 Bytes</td>
 </tr>
 </table>