Support second y axis for multiple measures

[codingfabi]

Is your feature request related to a problem? Please describe. If I want to display multiple percent measures with multiple absolute measures in the same chart, I need to assign the percentage measures to the second yAxis. However, this is not possible for multiple measures because the second yAxis only takes one selector.

Describe the solution you'd like I would expect both percent measures to be oriented at the same second yAxis.