Add ability to scroll to negative X and Y

[Monabr]

Hello.

It would be nice if I could scroll the chart to negative values. Because if it takes up part of the screen it sticks to X or Y and to make it centered on the screen I have to zoom it instead of just scrolling the whole chart to the center. This also applies to the Flame Chart which sticks to the X axis even though I want it to be centered on the screen.