docs: update README.md [skip ci]

Author: allcontributors[bot]

README.md

@@ -14,7 +14,7 @@
 [![black code style](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/ambv/black)
 
 <!-- ALL-CONTRIBUTORS-BADGE:START - Do not remove or modify this section -->
-[![All Contributors](https://img.shields.io/badge/all_contributors-53-orange.svg)](#-contributors)
+[![All Contributors](https://img.shields.io/badge/all_contributors-54-orange.svg)](#-contributors)
 <!-- ALL-CONTRIBUTORS-BADGE:END -->
 
 </div>
@@ -249,6 +249,7 @@ Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/d
       <td align="center" valign="top" width="14.28%"><a href="https://aniketsinghrawat.vercel.app/"><img src="https://avatars.githubusercontent.com/u/31622972?v=4?s=100" width="100px;" alt="Aniket Singh Rawat"/><br /><sub><b>Aniket Singh Rawat</b></sub></a><br /><a href="https://github.com/pybamm-team/PyBaMM/commits?author=dikwickley" title="Code">💻</a></td>
       <td align="center" valign="top" width="14.28%"><a href="https://github.com/jeromtom"><img src="https://avatars.githubusercontent.com/u/83979298?v=4?s=100" width="100px;" alt="Jerom Palimattom Tom"/><br /><sub><b>Jerom Palimattom Tom</b></sub></a><br /><a href="https://github.com/pybamm-team/PyBaMM/commits?author=jeromtom" title="Documentation">📖</a> <a href="https://github.com/pybamm-team/PyBaMM/commits?author=jeromtom" title="Code">💻</a> <a href="https://github.com/pybamm-team/PyBaMM/commits?author=jeromtom" title="Tests">⚠️</a></td>
       <td align="center" valign="top" width="14.28%"><a href="http://bradyplanden.github.io"><img src="https://avatars.githubusercontent.com/u/55357039?v=4?s=100" width="100px;" alt="Brady Planden"/><br /><sub><b>Brady Planden</b></sub></a><br /><a href="#example-BradyPlanden" title="Examples">💡</a></td>
+      <td align="center" valign="top" width="14.28%"><a href="https://github.com/arjxn-py"><img src="https://avatars.githubusercontent.com/u/104268427?v=4?s=100" width="100px;" alt="Arjun"/><br /><sub><b>Arjun</b></sub></a><br /><a href="#infra-arjxn-py" title="Infrastructure (Hosting, Build-Tools, etc)">🚇</a></td>
     </tr>
   </tbody>
 </table>