docs: add jhnns as a contributor (#912)

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

Author: allcontributors[bot]

.all-contributorsrc

@@ -1252,6 +1252,15 @@
       "contributions": [
         "test"
       ]
+    },
+    {
+      "login": "jhnns",
+      "name": "Johannes Ewald",
+      "avatar_url": "https://avatars.githubusercontent.com/u/781746?v=4",
+      "profile": "https://github.com/jhnns",
+      "contributions": [
+        "code"
+      ]
     }
   ],
   "contributorsPerLine": 7,

README.md

@@ -607,6 +607,7 @@ Thanks goes to these people ([emoji key][emojis]):
     <td align="center"><a href="https://github.com/sanchit121"><img src="https://avatars2.githubusercontent.com/u/30828115?v=4?s=100" width="100px;" alt=""/><br /><sub><b>sanchit121</b></sub></a><br /><a href="https://github.com/testing-library/react-testing-library/issues?q=author%3Asanchit121" title="Bug reports">🐛</a> <a href="https://github.com/testing-library/react-testing-library/commits?author=sanchit121" title="Code">💻</a></td>
     <td align="center"><a href="https://github.com/solufa"><img src="https://avatars.githubusercontent.com/u/9402912?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Solufa</b></sub></a><br /><a href="https://github.com/testing-library/react-testing-library/issues?q=author%3Asolufa" title="Bug reports">🐛</a> <a href="https://github.com/testing-library/react-testing-library/commits?author=solufa" title="Code">💻</a></td>
     <td align="center"><a href="https://codepen.io/ariperkkio/"><img src="https://avatars.githubusercontent.com/u/14806298?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Ari Perkkiö</b></sub></a><br /><a href="https://github.com/testing-library/react-testing-library/commits?author=AriPerkkio" title="Tests">⚠️</a></td>
+    <td align="center"><a href="https://github.com/jhnns"><img src="https://avatars.githubusercontent.com/u/781746?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Johannes Ewald</b></sub></a><br /><a href="https://github.com/testing-library/react-testing-library/commits?author=jhnns" title="Code">💻</a></td>
   </tr>
 </table>