docs: update README.md [skip ci]

Author: allcontributors[bot]

README.md

@@ -139,6 +139,7 @@ Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/d
  <td align="center"><a href="http://fb.me/yz"><img src="https://avatars3.githubusercontent.com/u/14841421?v=4" width="100px;" alt=""/><br /><sub><b>Jack Zhao</b></sub></a><br /><a href="https://github.com/testing-library/testing-library-docs/commits?author=bugzpodder" title="Documentation">📖</a></td>
  <td align="center"><a href="https://github.com/rkennel"><img src="https://avatars2.githubusercontent.com/u/28492538?v=4" width="100px;" alt=""/><br /><sub><b>Ryan Kennel</b></sub></a><br /><a href="https://github.com/testing-library/testing-library-docs/commits?author=rkennel" title="Documentation">📖</a></td>
  <td align="center"><a href="https://github.com/JesuHrz"><img src="https://avatars0.githubusercontent.com/u/28031187?v=4" width="100px;" alt=""/><br /><sub><b>Jesus Hernandez</b></sub></a><br /><a href="https://github.com/testing-library/testing-library-docs/commits?author=JesuHrz" title="Documentation">📖</a></td>
+ <td align="center"><a href="https://github.com/airjp73"><img src="https://avatars2.githubusercontent.com/u/25882770?v=4" width="100px;" alt=""/><br /><sub><b>Aaron Pettengill</b></sub></a><br /><a href="https://github.com/testing-library/testing-library-docs/commits?author=airjp73" title="Documentation">📖</a></td>
  </tr>
 </table>