docs: add Lukas-Kullmann as a contributor (#587)

* docs: update README.md

* docs: update .all-contributorsrc

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

Author: allcontributors[bot]

.all-contributorsrc

@@ -944,6 +944,16 @@
       "contributions": [
         "doc"
       ]
+    },
+    {
+      "login": "Lukas-Kullmann",
+      "name": "Lukas",
+      "avatar_url": "https://avatars0.githubusercontent.com/u/387547?v=4",
+      "profile": "https://github.com/Lukas-Kullmann",
+      "contributions": [
+        "code",
+        "test"
+      ]
     }
   ],
   "repoHost": "https://github.com"

README.md

@@ -254,6 +254,7 @@ Thanks goes to these people ([emoji key][emojis]):
     <td align="center"><a href="https://github.com/mzdunek93"><img src="https://avatars0.githubusercontent.com/u/10826511?v=4" width="100px;" alt=""/><br /><sub><b>Michał Zdunek</b></sub></a><br /><a href="https://github.com/testing-library/dom-testing-library/commits?author=mzdunek93" title="Code">💻</a></td>
     <td align="center"><a href="https://github.com/Lagily"><img src="https://avatars2.githubusercontent.com/u/42535205?v=4" width="100px;" alt=""/><br /><sub><b>Ali Nasserzadeh</b></sub></a><br /><a href="https://github.com/testing-library/dom-testing-library/commits?author=Lagily" title="Code">💻</a></td>
     <td align="center"><a href="https://darekkay.com"><img src="https://avatars0.githubusercontent.com/u/3101914?v=4" width="100px;" alt=""/><br /><sub><b>Darek Kay</b></sub></a><br /><a href="https://github.com/testing-library/dom-testing-library/commits?author=darekkay" title="Documentation">📖</a></td>
+    <td align="center"><a href="https://github.com/Lukas-Kullmann"><img src="https://avatars0.githubusercontent.com/u/387547?v=4" width="100px;" alt=""/><br /><sub><b>Lukas</b></sub></a><br /><a href="https://github.com/testing-library/dom-testing-library/commits?author=Lukas-Kullmann" title="Code">💻</a> <a href="https://github.com/testing-library/dom-testing-library/commits?author=Lukas-Kullmann" title="Tests">⚠️</a></td>
   </tr>
 </table>