docs: add RobbertWolfs as a contributor (kentcdodds#88)

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

.all-contributorsrc

@@ -208,6 +208,15 @@
       "contributions": [
         "test"
       ]
+    },
+    {
+      "login": "RobbertWolfs",
+      "name": "Robbert Wolfs",
+      "avatar_url": "https://avatars2.githubusercontent.com/u/12511178?v=4",
+      "profile": "https://github.com/RobbertWolfs",
+      "contributions": [
+        "doc"
+      ]
     }
   ],
   "contributorsPerLine": 7,

README.md

@@ -295,6 +295,7 @@ Thanks goes to these wonderful people
   </tr>
   <tr>
     <td align="center"><a href="http://frontendwizard.dev"><img src="https://avatars1.githubusercontent.com/u/1124448?v=4" width="100px;" alt=""/><br /><sub><b>Juliano Farias</b></sub></a><br /><a href="https://github.com/kentcdodds/bookshelf/commits?author=frontendwizard" title="Tests">⚠️</a></td>
+    <td align="center"><a href="https://github.com/RobbertWolfs"><img src="https://avatars2.githubusercontent.com/u/12511178?v=4" width="100px;" alt=""/><br /><sub><b>Robbert Wolfs</b></sub></a><br /><a href="https://github.com/kentcdodds/bookshelf/commits?author=RobbertWolfs" title="Documentation">📖</a></td>
   </tr>
 </table>