docs: add Dennis273 as a contributor for code (#581)

* docs: update README.md

* docs: update .all-contributorsrc

---------

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

.all-contributorsrc

@@ -739,6 +739,15 @@
         "code",
         "test"
       ]
+    },
+    {
+      "login": "Dennis273",
+      "name": "Dennis Chen",
+      "avatar_url": "https://avatars.githubusercontent.com/u/19815164?v=4",
+      "profile": "https://github.com/Dennis273",
+      "contributions": [
+        "code"
+      ]
     }
   ],
   "repoHost": "https://github.com",

README.md

@@ -1543,6 +1543,7 @@ Thanks goes to these people ([emoji key][emojis]):
       <td align="center" valign="top" width="14.28%"><a href="https://github.com/jakeboone02"><img src="https://avatars.githubusercontent.com/u/366438?v=4?s=100" width="100px;" alt="Jake Boone"/><br /><sub><b>Jake Boone</b></sub></a><br /><a href="https://github.com/testing-library/jest-dom/commits?author=jakeboone02" title="Code">💻</a> <a href="https://github.com/testing-library/jest-dom/commits?author=jakeboone02" title="Tests">⚠️</a></td>
       <td align="center" valign="top" width="14.28%"><a href="http://www.stekoe.de"><img src="https://avatars.githubusercontent.com/u/1809221?v=4?s=100" width="100px;" alt="Stephan Köninger"/><br /><sub><b>Stephan Köninger</b></sub></a><br /><a href="https://github.com/testing-library/jest-dom/issues?q=author%3ASteKoe" title="Bug reports">🐛</a> <a href="https://github.com/testing-library/jest-dom/commits?author=SteKoe" title="Code">💻</a></td>
       <td align="center" valign="top" width="14.28%"><a href="https://github.com/kryops"><img src="https://avatars.githubusercontent.com/u/1042594?v=4?s=100" width="100px;" alt="Michael Manzinger"/><br /><sub><b>Michael Manzinger</b></sub></a><br /><a href="https://github.com/testing-library/jest-dom/issues?q=author%3Akryops" title="Bug reports">🐛</a> <a href="https://github.com/testing-library/jest-dom/commits?author=kryops" title="Code">💻</a> <a href="https://github.com/testing-library/jest-dom/commits?author=kryops" title="Tests">⚠️</a></td>
+      <td align="center" valign="top" width="14.28%"><a href="https://github.com/Dennis273"><img src="https://avatars.githubusercontent.com/u/19815164?v=4?s=100" width="100px;" alt="Dennis Chen"/><br /><sub><b>Dennis Chen</b></sub></a><br /><a href="https://github.com/testing-library/jest-dom/commits?author=Dennis273" title="Code">💻</a></td>
     </tr>
   </tbody>
 </table>