Add UID as a classname to bar trace #7328

[gregdeback]

Feature

Scatter traces have always 3 classnames: trace scatter trace{UID} where UID is the trace unique ID (trace.uid).
Now bar traces can have it too: trace bars trace{UID}.

[alexcjohnson]

Curious what you want this for? We don’t generally consider DOM structure like this to be part of the public API so in principle it’s subject to change at any time, though in practice it has likely been very stable.

[gregdeback]

It's because I'm working on a project where we would like the hovered bar series to be highlighted (by changing the opacity of the others). It's easy to retrieve the UID of the hovered trace, so for scatter (& line) traces it's easy to access the <g>roup (using querySelector('.trace' + point.uid))... but not for bar traces.
Or maybe there is an easier way to retrieve the <g>roup from the hovered point (or its trace)?

[archmoj]

Suggested change

	- Add `trace{UID}` to bar traces as for scatter ones [[#7328](https://github.com/plotly/plotly.js/issues/7328)]
	- Add `trace{UID}` to bar, histogram, funnel and waterfall traces as for scatter ones [[#7328](https://github.com/plotly/plotly.js/issues/7328)],
	with thanks to @gregdeback for the contribution!