Ability to have labelLines attribute (with callback function) in PieCharts

[ramkumarkb]

It is usually good practice to have labels along with the pie-chart (instead of a separate legend). This visually helps the users to see the different fractions - instead of referring to the Pie and Legend separately.

As an example - https://echarts.apache.org/examples/en/editor.html?c=pie-labelLine-adjust
In this, the labelLines adapt to the length of the labels itself and therefore present a visually appealing pie chart with labels, with the colors of the labelLines matching that of the pie-section.

This is a suggested feature in the current chart.piechart