docs: add mathiassoeholm as a contributor (#724)

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

Author: superT999

.all-contributorsrc

@@ -1184,6 +1184,15 @@
       "contributions": [
         "doc"
       ]
+    },
+    {
+      "login": "mathiassoeholm",
+      "name": "Mathias",
+      "avatar_url": "https://avatars0.githubusercontent.com/u/1747242?v=4",
+      "profile": "https://github.com/mathiassoeholm",
+      "contributions": [
+        "doc"
+      ]
     }
   ],
   "contributorsPerLine": 7,

README.md

@@ -299,6 +299,7 @@ Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/d
     <td align="center"><a href="https://nickmccurdy.com/"><img src="https://avatars0.githubusercontent.com/u/927220?v=4" width="100px;" alt=""/><br /><sub><b>Nick McCurdy</b></sub></a><br /><a href="https://github.com/testing-library/testing-library-docs/commits?author=nickmccurdy" title="Documentation">📖</a> <a href="https://github.com/testing-library/testing-library-docs/pulls?q=is%3Apr+reviewed-by%3Anickmccurdy" title="Reviewed Pull Requests">👀</a> <a href="https://github.com/testing-library/testing-library-docs/commits?author=nickmccurdy" title="Code">💻</a></td>
     <td align="center"><a href="http://sudhanshu-ranjan.tech"><img src="https://avatars2.githubusercontent.com/u/22864071?v=4" width="100px;" alt=""/><br /><sub><b>Sudhanshu</b></sub></a><br /><a href="https://github.com/testing-library/testing-library-docs/commits?author=tsuki42" title="Documentation">📖</a></td>
     <td align="center"><a href="http://newrope.biz"><img src="https://avatars0.githubusercontent.com/u/58922379?v=4" width="100px;" alt=""/><br /><sub><b>Aleksandr Chernov</b></sub></a><br /><a href="https://github.com/testing-library/testing-library-docs/commits?author=aleks-rope" title="Documentation">📖</a></td>
+    <td align="center"><a href="https://github.com/mathiassoeholm"><img src="https://avatars0.githubusercontent.com/u/1747242?v=4" width="100px;" alt=""/><br /><sub><b>Mathias</b></sub></a><br /><a href="https://github.com/testing-library/testing-library-docs/commits?author=mathiassoeholm" title="Documentation">📖</a></td>
   </tr>
 </table>