Update jupyter.md

Added simple instructions for creating a Jupyter notebook file in the VSCode example.

runtime/reference/cli/jupyter.md

@@ -33,6 +33,7 @@ notebooks.
 
 - Install the
  [VSCode Jupyter extension](https://marketplace.visualstudio.com/items?itemName=ms-toolsai.jupyter)
+- Open or create a notebook file by opening the Command Palette (Ctrl+Shift+P) and selecting "Create: New Jupyter Notebook". This can be done manually by creating a file with the ".ipynb" file extension.
 - When on a new or existing Notebook, click creating a new Jupyter Notebook
  select "Jupyter kernels" and then select Deno