ui.table formatting background_color heatmap

[mattrunyon]

Support describing a column background_color as a heatmap. Probably use a dataclass passed to background_color.

We should offer auto max/min, users should be able to specify colorstops (e.g. "I want 0 to always be white"), users should be able to specify explicit max/min or columns as max/min. Basically very similar API to databar, but for heatmap.

[dsmmcken]

I get the argument for passing it to background_color, but I envisioned it more like databar which would be a mode.

I think it's important the client does the color interpolation in oklab space, and needs to accept multiple colors as an it's range.

It should also have good set of defaults like databar where simply passing mode="heatmap" or whatever automatically has a pretty gradient, auto min/auto max behaviour.

I don't know if it makes sense but it could be something set on text instead of background?