docs: update .all-contributorsrc

Author: allcontributors[bot]

.all-contributorsrc

@@ -308,6 +308,17 @@
         "ideas",
         "test"
       ]
+    },
+    {
+      "login": "steppi",
+      "name": "Albert Steppi",
+      "avatar_url": "https://avatars.githubusercontent.com/u/1953382?v=4",
+      "profile": "http://steppi.github.io",
+      "contributions": [
+        "code",
+        "ideas",
+        "test"
+      ]
     }
   ]
 }