docs: update README.md [skip ci]

README.md

@@ -138,6 +138,7 @@ Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/d
     <td align="center"><a href="https://github.com/victorcmoura"><img src="https://avatars1.githubusercontent.com/u/26290053?v=4" width="100px;" alt=""/><br /><sub><b>Victor Moura</b></sub></a><br /><a href="https://github.com/containrrr/watchtower/commits?author=victorcmoura" title="Tests">⚠️</a></td>
     <td align="center"><a href="https://github.com/mbrandau"><img src="https://avatars3.githubusercontent.com/u/12972798?v=4" width="100px;" alt=""/><br /><sub><b>Maximilian Brandau</b></sub></a><br /><a href="https://github.com/containrrr/watchtower/commits?author=mbrandau" title="Code">💻</a></td>
     <td align="center"><a href="https://github.com/aneisch"><img src="https://avatars1.githubusercontent.com/u/6991461?v=4" width="100px;" alt=""/><br /><sub><b>Andrew</b></sub></a><br /><a href="https://github.com/containrrr/watchtower/commits?author=aneisch" title="Documentation">📖</a></td>
+    <td align="center"><a href="https://github.com/sixcorners"><img src="https://avatars0.githubusercontent.com/u/585501?v=4" width="100px;" alt=""/><br /><sub><b>sixcorners</b></sub></a><br /><a href="https://github.com/containrrr/watchtower/commits?author=sixcorners" title="Documentation">📖</a></td>
   </tr>
 </table>