docs: add Semigradsky as a contributor (#772)

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

Author: allcontributors[bot]

.all-contributorsrc

@@ -1233,6 +1233,15 @@
       "contributions": [
         "bug"
       ]
+    },
+    {
+      "login": "Semigradsky",
+      "name": "Dmitry Semigradsky",
+      "avatar_url": "https://avatars3.githubusercontent.com/u/1198848?v=4",
+      "profile": "https://github.com/Semigradsky",
+      "contributions": [
+        "code"
+      ]
     }
   ],
   "repoHost": "https://github.com"

README.md

@@ -292,6 +292,7 @@ Thanks goes to these people ([emoji key][emojis]):
     <td align="center"><a href="https://github.com/winterlamon"><img src="https://avatars0.githubusercontent.com/u/16295605?v=4" width="100px;" alt=""/><br /><sub><b>Winter LaMon</b></sub></a><br /><a href="https://github.com/testing-library/dom-testing-library/commits?author=winterlamon" title="Code">💻</a> <a href="https://github.com/testing-library/dom-testing-library/commits?author=winterlamon" title="Tests">⚠️</a></td>
     <td align="center"><a href="http://victorandcode.com"><img src="https://avatars0.githubusercontent.com/u/18427801?v=4" width="100px;" alt=""/><br /><sub><b>Victor Cordova</b></sub></a><br /><a href="https://github.com/testing-library/dom-testing-library/commits?author=victorandcode" title="Code">💻</a> <a href="https://github.com/testing-library/dom-testing-library/commits?author=victorandcode" title="Tests">⚠️</a></td>
     <td align="center"><a href="https://github.com/slowselfip"><img src="https://avatars3.githubusercontent.com/u/9762906?v=4" width="100px;" alt=""/><br /><sub><b>slowselfip</b></sub></a><br /><a href="https://github.com/testing-library/dom-testing-library/issues?q=author%3Aslowselfip" title="Bug reports">🐛</a></td>
+    <td align="center"><a href="https://github.com/Semigradsky"><img src="https://avatars3.githubusercontent.com/u/1198848?v=4" width="100px;" alt=""/><br /><sub><b>Dmitry Semigradsky</b></sub></a><br /><a href="https://github.com/testing-library/dom-testing-library/commits?author=Semigradsky" title="Code">💻</a></td>
   </tr>
 </table>