Feature request: Add gallery to docs

[cvanelteren]

We should show case the power of UlraPlot for casual browsers. I think something similar to a gallery overview that should entice browsers and viewer and perhaps inspire to make new complicated plots.

The plots should focus:

• ...on the core value that we add in UltraPlot
• ...unique features that UltraPlot adds (layout sharing, legends, abc etc)
• ...[?]

I was thinking over leveraging the existing jupytext and linking them immediately, but perhaps a more curated list is better.