Remove JupyterLab dependency in jupyterlab_widgets
Remove JupyterLab dependency in jupyterlab_widgets

Even though jupyterlab_widgets is useless without JupyterLab, it is only
a small Python package (that don't need JupyterLab) and some static
files installed in the right path (share/jupyter/labextensions). I would
then expect it to not depend on JupyterLab.

This will allow other widgets extension to depend on the jupyterlab_widget
package so that those widgets extensions can work on JupyterLab out of
the box, without them depending on JupyterLab.

Signed-off-by: martinRenou <a8278cece597ec79cc59974d3d55dbb79bb38416@gmail.com>

ipython/ipywidgets,jupyter-widgets/ipywidgets,jupyter-widgets/ipywidgets,ipython/ipywidgets,jupyter-widgets/ipywidgets,ipython/ipywidgets,ipython/ipywidgets,ipython/ipywidgets,jupyter-widgets/ipywidgets