docs: add @firefrei as a contributor

.all-contributorsrc

@@ -3721,6 +3721,15 @@
       "contributions": [
         "code"
       ]
+    },
+    {
+      "login": "firefrei",
+      "name": "Matthias Frei",
+      "avatar_url": "https://avatars.githubusercontent.com/u/12660103?v=4",
+      "profile": "https://www.frei.media/",
+      "contributions": [
+        "code"
+      ]
     }
   ]
 }

CONTRIBUTORS.md

@@ -532,6 +532,7 @@ Thanks goes to all of these wonderful people ([emoji key](https://github.com/ken
       <td align="center" valign="top" width="14.28%"><a href="http://nevets82.github.io/"><img src="https://avatars.githubusercontent.com/u/4462739?v=4?s=110" width="110px;" alt="Steven"/><br /><sub><b>Steven</b></sub></a><br /><a href="https://github.com/snipe/snipe-it/commits?author=Nevets82" title="Code">💻</a></td>
       <td align="center" valign="top" width="14.28%"><a href="https://mateusvillar.com/"><img src="https://avatars.githubusercontent.com/u/29017267?v=4?s=110" width="110px;" alt="Mateus Villar"/><br /><sub><b>Mateus Villar</b></sub></a><br /><a href="https://github.com/snipe/snipe-it/commits?author=Mateus-Romera" title="Code">💻</a></td>
       <td align="center" valign="top" width="14.28%"><a href="https://github.com/mzack5020"><img src="https://avatars.githubusercontent.com/u/12749393?v=4?s=110" width="110px;" alt="Matthew Zackschewski"/><br /><sub><b>Matthew Zackschewski</b></sub></a><br /><a href="https://github.com/snipe/snipe-it/commits?author=mzack5020" title="Code">💻</a></td>
+      <td align="center" valign="top" width="14.28%"><a href="https://www.frei.media/"><img src="https://avatars.githubusercontent.com/u/12660103?v=4?s=110" width="110px;" alt="Matthias Frei"/><br /><sub><b>Matthias Frei</b></sub></a><br /><a href="https://github.com/snipe/snipe-it/commits?author=firefrei" title="Code">💻</a></td>
     </tr>
   </tbody>
 </table>