getBottomSpace() returns incorrect Y Coordinate in Modal

[kingmeers]

Firstly, this is a great component!

Secondly, I understand the reasoning behind adding getBottomSpace() but it doesn't take into consideration whether or not the view is inside a modal, which overlays any tabbed navigation.

I recommend adding a final prop to ensure this is fixed for future issues, let me know if you'd like me to make a PR.

Thank you again!

Samir