make FigureWidget resizing responsive

[Alexboiboi]

Hi there,

As suggested by @nicolaskruchten I am open this issue to address FigureWidget specific resizing challenges.

As of the latest 5.12 release the resizing of a plotly FigureWidget is resolved:

import plotly.graph_objects as go

fig = go.FigureWidget()
fig

• FigureWidget: resizing can only expand but cannot shrink #3689

But the issue remains when the widget is in another widget container.

import plotly.graph_objects as go
import ipywidgets as ipw

fig = go.FigureWidget()
ipw.VBox([fig])

• There is a similar issue with bqplot that was adresssed by @mariobuikhuizen [fix: display and resize plots when not in a lumino context bqplot/bqplot#1531], maybe this is a good starting point (see @maartenbreddels comment Compatibility with ipywidgets v8 #3930 (comment))

Also it would really help to make responsive webapps with the ipywidgets ecosystem if the FigureWidget would also resize vertically to the available space inside its container.

No one on the Plotly team is really actively working on the Widget side of things so PRs are very welcome :)
I would gladly contribute but my knowledge in javascript is quasi non-existent^^, so I hope some of you are able to help out here.

Best regards, Alex-