axis.settings.labels.fill does not support function

[peol]

🐛 Bug report

As is common praxis with picasso.js nowadays, I expect to pass in a function to a property to programmatically control values in components.

This is not true for the axis labels fill property currently.

Steps to Reproduce

1. Create an axis:

{
  type: 'axis',
  scale: 'y',
  settings: {
    labels: {
      _fill: 'blue',
      fill: v => (console.log(v), v < 50 ? 'red' : 'blue')
    }
  }
}

2. Verify that the axis label is still black, and no values are logged to the console

Expected behavior

I expect to be able to control the value programmatically.

Actual behavior

It only takes a hardcoded (string) value.

Versions

• picasso.js: 0.13.2
• Browser: ?