Smooth line chart support

[arikfr]

In Plotly it's probably Spline.

Blocked by #2988.

[kocsmy]

Maybe we could add other options, too?

[deecay]

Area chart with spline would look like this.

[deecay]

Should this be part of "General" setting? or "Series" setting?

[kravets-levko]

@deecay I think it should be both: general setting (which becomes available only for line/area chart types), and ability to override it for each serie - similar to how chart type works

[arikfr]

@deecay it can probably be a new chart type (like line or area), and then it will be in both, as @kravets-levko suggested.

[veshus]

Is any chance to implement this feature?

[guidopetri]

It's on our list, but given the nature of open source work it might be a while before it gets implemented. Happy to accept PRs introducing this functionality though!