docs: update index.md [skip ci]

Author: allcontributors[bot]

index.md

@@ -195,6 +195,7 @@ math: true
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     <td align="center"><a href="http://fbcf.xyz"><img src="https://avatars.githubusercontent.com/u/46428367?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Felix</b></sub></a><br /><a href="https://github.com/CSRG-Group/dcs-notes.github.io/issues?q=author%3Aefbicief" title="Bug reports">🐛</a></td>
+    <td align="center"><a href="https://tomff.com"><img src="https://avatars.githubusercontent.com/u/15079464?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Tomás F.</b></sub></a><br /><a href="#design-tomasff" title="Design">🎨</a></td>
   </tr>
 </table>