docs: add Letalus as a contributor (#135)

* docs: update README.md [skip ci]

* docs: update .all-contributorsrc [skip ci]

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

Author: allcontributors[bot]

.all-contributorsrc

@@ -90,7 +90,8 @@
       "avatar_url": "https://avatars.githubusercontent.com/u/41230136?v=4",
       "profile": "https://github.com/Letalus",
       "contributions": [
-        "bug"
+        "bug",
+        "translation"
       ]
     }
   ],

README.md

@@ -411,7 +411,7 @@ Many thanks to these wonderful people ([emoji key](https://allcontributors.org/d
     <td align="center"><a href="https://github.com/avi-yadav"><img src="https://avatars.githubusercontent.com/u/7314430?v=4?s=50" width="50px;" alt=""/><br /><sub><b>avi-yadav</b></sub></a><br /><a href="https://github.com/fluttercandies/flutter_wechat_assets_picker/commits?author=avi-yadav" title="Code">💻</a></td>
   </tr>
   <tr>
-    <td align="center"><a href="https://github.com/Letalus"><img src="https://avatars.githubusercontent.com/u/41230136?v=4?s=50" width="50px;" alt=""/><br /><sub><b>Letalus</b></sub></a><br /><a href="https://github.com/fluttercandies/flutter_wechat_assets_picker/issues?q=author%3ALetalus" title="Bug reports">🐛</a></td>
+    <td align="center"><a href="https://github.com/Letalus"><img src="https://avatars.githubusercontent.com/u/41230136?v=4?s=50" width="50px;" alt=""/><br /><sub><b>Letalus</b></sub></a><br /><a href="https://github.com/fluttercandies/flutter_wechat_assets_picker/issues?q=author%3ALetalus" title="Bug reports">🐛</a> <a href="#translation-Letalus" title="Translation">🌍</a></td>
   </tr>
 </table>