docs: add G-Rath as a contributor for code, test (#1014)

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

Author: allcontributors[bot]

.all-contributorsrc

@@ -1396,6 +1396,16 @@
       "contributions": [
         "doc"
       ]
+    },
+    {
+      "login": "G-Rath",
+      "name": "Gareth Jones",
+      "avatar_url": "https://avatars.githubusercontent.com/u/3151613?v=4",
+      "profile": "https://github.com/G-Rath",
+      "contributions": [
+        "code",
+        "test"
+      ]
     }
   ],
   "repoHost": "https://github.com"

README.md

@@ -314,6 +314,7 @@ Thanks goes to these people ([emoji key][emojis]):
   <tr>
     <td align="center"><a href="https://github.com/amitmiran137"><img src="https://avatars.githubusercontent.com/u/47772523?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Amit Miran</b></sub></a><br /><a href="#infra-amitmiran137" title="Infrastructure (Hosting, Build-Tools, etc)">🚇</a></td>
     <td align="center"><a href="https://github.com/leschdom"><img src="https://avatars.githubusercontent.com/u/62334278?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Dominik Lesch</b></sub></a><br /><a href="https://github.com/testing-library/dom-testing-library/commits?author=leschdom" title="Documentation">📖</a></td>
+    <td align="center"><a href="https://github.com/G-Rath"><img src="https://avatars.githubusercontent.com/u/3151613?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Gareth Jones</b></sub></a><br /><a href="https://github.com/testing-library/dom-testing-library/commits?author=G-Rath" title="Code">💻</a> <a href="https://github.com/testing-library/dom-testing-library/commits?author=G-Rath" title="Tests">⚠️</a></td>
   </tr>
 </table>