Add large note to the 8.x documentation indicating the new ipywidgets version.
Add large note to the 8.x documentation indicating the new ipywidgets version.

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