Hover events on the lines themselves

A dash community user brought this up https://community.plot.ly/t/linking-scattermapbox-lines-to-other-data-with-callbacks/5449

They would like some type of event be fired when hovering over lines instead of just points:

I would also like to raise an appeal for maps of lines being treated as actual lines rather than collections of points. It seems like the callbacks are only firing above the component points, rather than over the line itself, which is confusing to an end user.

首先跟踪 scattermapbox 的悬停处理及其回调事件路径；该 issue 未指出具体的文件或测试。将现有的 point-hover 行为与所请求的 line-hover 行为进行比较，并在悬停一条线时能够触发事件，而不仅仅是悬停其组成点时能够触发事件后，视为工作完成。