add kostyafarber as a contributor for code (jupyterlab#1190)

* update README.md [skip ci]

* update .all-contributorsrc [skip ci]

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

Author: allcontributors[bot]

.all-contributorsrc

@@ -256,6 +256,15 @@
       "contributions": [
         "code"
       ]
+    },
+    {
+      "login": "kostyafarber",
+      "name": "Kostya Farber",
+      "avatar_url": "https://avatars.githubusercontent.com/u/73378227?v=4",
+      "profile": "https://kostyafarber.github.io/",
+      "contributions": [
+        "code"
+      ]
     }
   ],
   "contributorsPerLine": 7,