docs: add JaapCTJ as a contributor for code (#903)

Author: allcontributors[bot]

.all-contributorsrc

@@ -315,6 +315,15 @@
       "contributions": [
         "doc"
       ]
+    },
+    {
+      "login": "JaapCTJ",
+      "name": "JaapCTJ",
+      "avatar_url": "https://avatars.githubusercontent.com/u/157970664?v=4",
+      "profile": "https://github.com/JaapCTJ",
+      "contributions": [
+        "code"
+      ]
     }
   ],
   "contributorsPerLine": 8,

README.md

@@ -280,6 +280,7 @@ Thanks goes to these wonderful people:
     </tr>
     <tr>
       <td align="center" valign="top" width="12.5%"><a href="https://github.com/jestover"><img src="https://avatars.githubusercontent.com/u/11298484?v=4?s=100" width="100px;" alt="Joseph Stover"/><br /><sub><b>Joseph Stover</b></sub></a><br /><a href="https://github.com/py-econometrics/pyfixest/commits?author=jestover" title="Documentation">📖</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/JaapCTJ"><img src="https://avatars.githubusercontent.com/u/157970664?v=4?s=100" width="100px;" alt="JaapCTJ"/><br /><sub><b>JaapCTJ</b></sub></a><br /><a href="https://github.com/py-econometrics/pyfixest/commits?author=JaapCTJ" title="Code">💻</a></td>
     </tr>
   </tbody>
 </table>