README.notebooks: add note about creating ipykernel

Author: dlech

pybricksdev/README.notebooks.md

@@ -5,4 +5,5 @@ Here are some tips on using `pybricksdev` with Jupyter notebooks.
 - Create a virtual environment for hosting the kernel.
 - Required packages: `pybricksdev`, `notebook`, `ipykernel`, `ipywidgets`
 - Enable widgets for progress bars: `jupyter nbextension enable --py widgetsnbextension`
+- Create a named kernel: `python -m ipykernel install --user --name=pybricksdev`
 - Start a notebook server: `jupyter notebook`