How to fill color only below the zero line and set different line color below the zero line

Expectation is to set the different color for line just below the zero line and fill color only below the zero line

## What did you do?

I have tried
`dataset.fillFormatter = DefaultFillFormatter { _, _ in
return CGFloat(uiView.leftAxis.axisMaximum)
}`

## What did you expect to happen?

Expectation is to change line color just below the zero line and only fill the color just below zero line

## DGCharts Environment

**DGCharts version/Branch/Commit Number:**
**Xcode version:14.2**
**Swift version:5.0**
**Platform(s) running DGCharts:iOS**
**macOS version running Xcode:12.6.3**

## Demo Project

ℹ Please link to or upload a project we can download that reproduces the issue.