docs: add MMartyn as a contributor for code (#3596)

* docs: update README.md [skip ci]

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

---------

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

.all-contributorsrc

@@ -520,6 +520,15 @@
       "contributions": [
         "code"
       ]
+    },
+    {
+      "login": "MMartyn",
+      "name": "Matt Martyn",
+      "avatar_url": "https://avatars.githubusercontent.com/u/1448102?v=4",
+      "profile": "https://github.com/MMartyn",
+      "contributions": [
+        "code"
+      ]
     }
   ],
   "contributorsPerLine": 7,

README.md

@@ -415,6 +415,7 @@ Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/d
     </tr>
     <tr>
       <td align="center" valign="top" width="14.28%"><a href="https://github.com/devumesh"><img src="https://avatars.githubusercontent.com/u/58872100?v=4?s=100" width="100px;" alt="Umesh Balamurugan"/><br /><sub><b>Umesh Balamurugan</b></sub></a><br /><a href="https://github.com/flipt-io/flipt/commits?author=devumesh" title="Code">💻</a></td>
+      <td align="center" valign="top" width="14.28%"><a href="https://github.com/MMartyn"><img src="https://avatars.githubusercontent.com/u/1448102?v=4?s=100" width="100px;" alt="Matt Martyn"/><br /><sub><b>Matt Martyn</b></sub></a><br /><a href="https://github.com/flipt-io/flipt/commits?author=MMartyn" title="Code">💻</a></td>
     </tr>
   </tbody>
 </table>