Add CSS to allow scrolling of ipywidget

[gabalafou]

This PR addresses one of the issues in #1740: missing horizontal scrollbar.

Changes:

• Add CSS rule to allow scrolling
• Add ipywidgets example to the examples/pydata page

[gabalafou]

Related:

• FIX: style table generated by myst-NB #1041

1041 and this PR address two related but different scenarios. They both deal with notebook cell outputs. But this PR deals specifically when the cell output uses ipywidgets.

1041 put an overflow-x: auto rule on notebook cell outputs rendered to HTML by myst-nb because otherwise, the default value of the output div would have overflow: visible, and wide tables inside the output div would cause the entire page to expand so the user would have to scroll the entire page horizontally. (Note: nbsphinx adds overflow: auto by default.)

This PR, on the other hand, has to override an overflow: hidden rule put on a container div via ipywidgets (via Lumino), regardless of whether the widget is rendered to HTML by myst-nb or nbsphinx.

[gabalafou]

self-review

[gabalafou]

I'm not entirely sure if I should set auto for both x and y or just x, but I decided to follow JupyterLab's lead, though to be honest I'm not entirely sure if the scenario described in jupyterlab/jupyterlab#6104 is applicable or not to sites built with PyData Sphinx Theme.

[gabalafou]

Note: I tested that this works for both nbsphinx and myst-nb (works = allows horizontal scrolling for wide table inside an ipywidget).

I'm wondering if there's some way to test this automatically, or if we could build two example pages from the same identical notebook, one through myst-nb and the other through nbsphinx.

[Carreau]

Ok, let's get this one in to get feedback