Support custom size

[MarcSkovMadsen]

Motivated by usage in data apps in general and #33 in particular, I would like to add a request for supporting custom sizing.

Currently the height is fixed at 10 rows (273px). This might be great for notebook usage, but for usage in Panel/ Shiny/ Solara/ Voila data apps its quite limited.

From the Panel perspective the best would be to support the widget.layout.height and widget.layout.width attributes like many other anywidgets/ ipywidgets does. We would like to be able to specify widget.layout.height="100%" to enable the Panel wrapping element to control the height.