docs: add merceyz as a contributor (#53)

* docs: update README.md

* docs: update .all-contributorsrc


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

Author: allcontributors[bot]

.all-contributorsrc

@@ -87,7 +87,8 @@
       "avatar_url": "https://avatars0.githubusercontent.com/u/3842800?v=4",
       "profile": "https://github.com/merceyz",
       "contributions": [
-        "code"
+        "code",
+        "test"
       ]
     },
     {

README.md

@@ -478,7 +478,7 @@ Thanks goes to these people ([emoji key][emojis]):
     <td align="center"><a href="http://andreneves.work"><img src="https://avatars2.githubusercontent.com/u/3869532?v=4" width="100px;" alt="André Neves"/><br /><sub><b>André Neves</b></sub></a><br /><a href="https://github.com/babel-utils/babel-plugin-tester/commits?author=andrefgneves" title="Code">💻</a> <a href="https://github.com/babel-utils/babel-plugin-tester/commits?author=andrefgneves" title="Tests">⚠️</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://github.com/merceyz"><img src="https://avatars0.githubusercontent.com/u/3842800?v=4" width="100px;" alt="Kristoffer K."/><br /><sub><b>Kristoffer K.</b></sub></a><br /><a href="https://github.com/babel-utils/babel-plugin-tester/commits?author=merceyz" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/merceyz"><img src="https://avatars0.githubusercontent.com/u/3842800?v=4" width="100px;" alt="Kristoffer K."/><br /><sub><b>Kristoffer K.</b></sub></a><br /><a href="https://github.com/babel-utils/babel-plugin-tester/commits?author=merceyz" title="Code">💻</a> <a href="https://github.com/babel-utils/babel-plugin-tester/commits?author=merceyz" title="Tests">⚠️</a></td>
     <td align="center"><a href="https://github.com/lifeart"><img src="https://avatars2.githubusercontent.com/u/1360552?v=4" width="100px;" alt="Alex Kanunnikov"/><br /><sub><b>Alex Kanunnikov</b></sub></a><br /><a href="https://github.com/babel-utils/babel-plugin-tester/commits?author=lifeart" title="Code">💻</a> <a href="https://github.com/babel-utils/babel-plugin-tester/commits?author=lifeart" title="Tests">⚠️</a></td>
   </tr>
 </table>