[Barchart] Style update - exploration for borders

[gvnmagni]

Border between elements on stacked bars

I would introduce a separation between bars so that we can improve the contrast between them and make them more accessible. We would then need a border of 1px of stroke-width, colored as the chart background, between all stacked bars

Bar border

Let's try to introduce a 1px border to all bars, this border needs to adapt to dark/light mode. So I would suggest a colors.fullShade border at 0.15 opacity on light mode, while 0.20 opacity on dark mode. (if possible, if we need to use only one value for opacity let's use 0.15)

Rounded corners

This option needs absolutely to be evaluate, I would try to introduce a rounded corner on all bars with a radius of 2px. I am very conflicted about this and I am not sure of the final result but it's worth to be explored and evaluated