Problem selecting bubbles on the same xIndex

[chuynadamas]

Hi @danielgindi and @liuxuan30 again, thank you for this amazing job!

I found a little issue here, when you have a chart with some bubbles at the same xIndex, something like that, you are not able to select all of them.

I did a little research and i discover that the following comparison on ChartDataSet.swift the problem

                    if abs(value.y - yValue) < abs(closestYValue - yValue)
                    {
                        closestYValue = yValue
                        closestYIndex = closest
                    }

If we add an equal = now we are able to select every bubble.

                    if abs(value.y - yValue) <= abs(closestYValue - yValue)
                    {
                        closestYValue = yValue
                        closestYIndex = closest
                    }

[liuxuan30]

sounds like you solved it? PR welcome :)