[Feature] Hyperlink/anchor support for pie charts

What problem does this feature solve?

Clicking a pie chart section or a legend entry should be able to take the user to a specified URL. I render my SVGs on the server, and browser Javascript is not strictly necessary for this feature, I currently achieve it by wrapping the sections and labels in <a xlink:href="${link}">…</a>.

This potentially could be extended to some other chart types.

What does the proposed API look like?

Not having much eCharts experience, I can only propose a suboptimal API. In my case it looks like this:

{
  "dataset": { "source": [["Company 1", 60, "/companies/1"], ["Company 2", 40, "/companies/2"]] }
}

Of course a different configuration option could be used to specify the mapping of labels to URLs in a more generic way, reusable by other types of charts.