📚 Add felixonmars as a contributor for code (#404)

* update README.md

* update .all-contributorsrc

---------

Co-authored-by: allcontributors[bot] <46447321+allcontributors[bot]@users.noreply.github.com>

.all-contributorsrc

@@ -235,6 +235,15 @@
       "contributions": [
         "bug"
       ]
+    },
+    {
+      "login": "felixonmars",
+      "name": "Felix Yan",
+      "avatar_url": "https://avatars.githubusercontent.com/u/1006477?v=4",
+      "profile": "https://github.com/felixonmars",
+      "contributions": [
+        "code"
+      ]
     }
   ],
   "contributorsPerLine": 7,

README.md

@@ -130,6 +130,7 @@ Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/d
       <td align="center" valign="top" width="14.28%"><a href="http://cnx.gdn"><img src="https://avatars.githubusercontent.com/u/13689192?v=4?s=100" width="100px;" alt="Nguyễn Gia Phong"/><br /><sub><b>Nguyễn Gia Phong</b></sub></a><br /><a href="https://github.com/roniemartinez/latex2mathml/issues?q=author%3AMcSinyx" title="Bug reports">🐛</a> <a href="https://github.com/roniemartinez/latex2mathml/commits?author=McSinyx" title="Code">💻</a> <a href="https://github.com/roniemartinez/latex2mathml/commits?author=McSinyx" title="Tests">⚠️</a></td>
       <td align="center" valign="top" width="14.28%"><a href="https://cdelker.github.io"><img src="https://avatars.githubusercontent.com/u/44102190?v=4?s=100" width="100px;" alt="Collin Delker"/><br /><sub><b>Collin Delker</b></sub></a><br /><a href="https://github.com/roniemartinez/latex2mathml/issues?q=author%3Acdelker" title="Bug reports">🐛</a></td>
       <td align="center" valign="top" width="14.28%"><a href="https://github.com/jiotv321"><img src="https://avatars.githubusercontent.com/u/118644533?v=4?s=100" width="100px;" alt="jiotv321"/><br /><sub><b>jiotv321</b></sub></a><br /><a href="https://github.com/roniemartinez/latex2mathml/issues?q=author%3Ajiotv321" title="Bug reports">🐛</a></td>
+      <td align="center" valign="top" width="14.28%"><a href="https://github.com/felixonmars"><img src="https://avatars.githubusercontent.com/u/1006477?v=4?s=100" width="100px;" alt="Felix Yan"/><br /><sub><b>Felix Yan</b></sub></a><br /><a href="https://github.com/roniemartinez/latex2mathml/commits?author=felixonmars" title="Code">💻</a></td>
     </tr>
   </tbody>
 </table>