Fill LineSeries below option.

[ragiovan]

How to reproduce?

Have a graph that is negative based for filling:

-If there was a graph with the y axis from -174 to -130, filling produces a fill above the line. A fill for below the line is better in probably most cases where the user has the y axis limits from -174 to -130.

I understand the reason for the current implementation, as the bound can be from the line to the x-axis. An increased functionality could allow the other end of the y bounds be from some stated negative value, or just -Int.MinValue for example, so that we can still fill below.

I am using

Live-Charts Version	Live-Charts 2
.Net Version	.Net Maui 6
Android	Android 13