docs: add maddingo as a contributor for code (#454)

* docs: update CONTRIBUTORS.md [skip ci]

* docs: update .all-contributorsrc [skip ci]

---------

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

.all-contributorsrc

@@ -175,6 +175,15 @@
       "contributions": [
         "ideas"
       ]
+    },
+    {
+      "login": "maddingo",
+      "name": "Martin Goldhahn",
+      "avatar_url": "https://avatars.githubusercontent.com/u/362120?v=4",
+      "profile": "https://github.com/maddingo",
+      "contributions": [
+        "code"
+      ]
     }
   ]
 }

CONTRIBUTORS.md

@@ -1,5 +1,5 @@
 <!-- ALL-CONTRIBUTORS-BADGE:START - Do not remove or modify this section -->
-[![All Contributors](https://img.shields.io/badge/all_contributors-18-orange.svg?style=flat-square)](#contributors-)
+[![All Contributors](https://img.shields.io/badge/all_contributors-19-orange.svg?style=flat-square)](#contributors-)
 <!-- ALL-CONTRIBUTORS-BADGE:END -->
 ## Contributors ✨
 
@@ -33,6 +33,7 @@ Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/d
       <td align="center" valign="top" width="14.28%"><a href="https://github.com/AbdelHajou"><img src="https://avatars.githubusercontent.com/u/62144407?v=4?s=100" width="100px;" alt="Abdel Hajou"/><br /><sub><b>Abdel Hajou</b></sub></a><br /><a href="#ideas-AbdelHajou" title="Ideas, Planning, & Feedback">🤔</a></td>
       <td align="center" valign="top" width="14.28%"><a href="https://www.hermanbarrantes.dev/"><img src="https://avatars.githubusercontent.com/u/1646195?v=4?s=100" width="100px;" alt="Herman Barrantes"/><br /><sub><b>Herman Barrantes</b></sub></a><br /><a href="#ideas-barrantesgerman" title="Ideas, Planning, & Feedback">🤔</a></td>
       <td align="center" valign="top" width="14.28%"><a href="https://andresalmiray.com/"><img src="https://avatars.githubusercontent.com/u/13969?v=4?s=100" width="100px;" alt="Andres Almiray"/><br /><sub><b>Andres Almiray</b></sub></a><br /><a href="#ideas-aalmiray" title="Ideas, Planning, & Feedback">🤔</a></td>
+      <td align="center" valign="top" width="14.28%"><a href="https://github.com/maddingo"><img src="https://avatars.githubusercontent.com/u/362120?v=4?s=100" width="100px;" alt="Martin Goldhahn"/><br /><sub><b>Martin Goldhahn</b></sub></a><br /><a href="https://github.com/mthmulders/mcs/commits?author=maddingo" title="Code">💻</a></td>
     </tr>
   </tbody>
 </table>