Fill frame withzoom (i.e. keep image apect ratio of image fixed)

[alex-s-gardner]

When an extent is defined to zoom into the aspect ratio of the displayed image changes. I think this should be changed such that the zoomed image always fills the frame. Otherwise the area of display keeps changing and looks hacky.

[rafaqz]

Should be easy to fix, have a go.

[alex-s-gardner]

Looking through the code I can't seem to find where a zoom rectangle triggers a response.

[rafaqz]

Tyler.jl/src/Tyler.jl

Lines 138 to 142 in 346b2c7

	on(axis.finallimits) do extent
	isopen(screen) || return
	update_tiles!(tyler, extent)
	return
	end

Although note that here the extent is probably a GeometryBasics Rect, but we can convert that to an extent