Stacked Col Chart - Display Sum of Values #3457

• I have searched the issues of this repository and believe that this is not a duplicate.

What problem does this feature solve?

I would like to be able to display the sum of the values in a stacked column or bar chart. This would allow for a more extensive use of the framework in a business use case

What does the proposed API look like?

I would allow it to be a method associated to the label. I would not know how to implement it yet as i am new to the repo and the antv enviroment.

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