docs: add just-boris as a contributor (#279)

* 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

@@ -512,6 +512,17 @@
       "contributions": [
         "test"
       ]
+    },
+    {
+      "login": "just-boris",
+      "name": "Boris Serdiuk",
+      "avatar_url": "https://avatars2.githubusercontent.com/u/812240?v=4",
+      "profile": "https://twitter.com/boriscoder",
+      "contributions": [
+        "bug",
+        "code",
+        "test"
+      ]
     }
   ],
   "repoHost": "https://github.com",

README.md

@@ -1162,6 +1162,7 @@ Thanks goes to these people ([emoji key][emojis]):
   <tr>
     <td align="center"><a href="http://katieboedges.com/"><img src="https://avatars1.githubusercontent.com/u/8322476?v=4" width="100px;" alt=""/><br /><sub><b>Katie Boedges</b></sub></a><br /><a href="#infra-kboedges" title="Infrastructure (Hosting, Build-Tools, etc)">🚇</a></td>
     <td align="center"><a href="https://github.com/brrianalexis"><img src="https://avatars2.githubusercontent.com/u/51463930?v=4" width="100px;" alt=""/><br /><sub><b>Brian Alexis</b></sub></a><br /><a href="https://github.com/testing-library/jest-dom/commits?author=brrianalexis" title="Tests">⚠️</a></td>
+    <td align="center"><a href="https://twitter.com/boriscoder"><img src="https://avatars2.githubusercontent.com/u/812240?v=4" width="100px;" alt=""/><br /><sub><b>Boris Serdiuk</b></sub></a><br /><a href="https://github.com/testing-library/jest-dom/issues?q=author%3Ajust-boris" title="Bug reports">🐛</a> <a href="https://github.com/testing-library/jest-dom/commits?author=just-boris" title="Code">💻</a> <a href="https://github.com/testing-library/jest-dom/commits?author=just-boris" title="Tests">⚠️</a></td>
   </tr>
 </table>