Update Installation

In JupyterLab 3, the enabling command is is sightly different

Author: dialvarezs

docs/installation.rst

@@ -14,27 +14,42 @@ Prerequisites
 Installation Step 1 (Installing the plugin itself)
 --------------------------------------------------
 
-Option 1) With Pip
-~~~~~~~~~~~~~~~~~~
+1.1 Installing the extension
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+With Pip:
 
 .. code-block:: bash
 
     pip install jupyterlab_code_formatter
-    jupyter serverextension enable --py jupyterlab_code_formatter
 
-Option 2) With Conda
-~~~~~~~~~~~~~~~~~~~~
+With Conda:
 
 .. code-block:: bash
 
     conda install -c conda-forge jupyterlab_code_formatter
+    
+1.2 Enabling the Extension
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+If you are using JupyterLab >= 3.0.0
+
+.. code-block:: bash
+    
+    jupyter server extension enable jupyterlab_code_formatter
+    # if you installed the plugin with pip and using --user, you need to add it here as well
+    jupyter server extension enable --user jupyterlab_code_formatter
+    
+...Or if you are still using JupyterLab < 3.0.0
+
+.. code-block:: bash
+    
     jupyter serverextension enable --py jupyterlab_code_formatter
 
+
 .. important::
     You will also need to install a code formatter for this plugin to work. The default formatter for Python are :code:`isort` and :code:`black`, and :code:`formatR` for R. Installing these would be a good place to start.
 
-There is a chance you will observe a warning message when running :code:`jupyter serverextension enable --py jupyterlab_code_formatter`, this should be safe to ignore for now (see this `issue`_).
-
 Also for users that haven't upgraded JupyterLab to version 3.0.0+, you will also need to run :code:`jupyter labextension install @ryantam626/jupyterlab_code_formatter`.
 
 Installation Step 2 (Installing a supported code formatter)