fix(jupyter-config): fix structure of jupyter-config directory

previously you needed to run "jupyter serverextension enable --py jupyterlab_s3_browser" to install
the serverextension

Author: reevejd

jupyter-config/jupyter_notebook_config.d/jupyterlab_s3_browser.json

@@ -0,0 +1,7 @@
+{
+  "NotebookApp": {
+    "nbserver_extensions": {
+      "jupyterlab_s3_browser": true
+    }
+  }
+}