fix ROI shift issue when saving svg

[wilsonGen]

Fix ROI shift issue when saving svg:

Issue:
When the IGV browser is not stick to the left of the web page, the saved SVG will have the ROI shifted:
how the IGV place in the webpage:

the output SVG from IGV:

If the IGV browser is stick to the left of the webpage like this👇, then the ROI in SVG will be normal

Work around:
Minus the columnContainer's clientX when rendering SVG rect of ROI instead of just using the regionElement's clientX

[turner]

@wilsonGen functionally it looks correct. It might be a bit cleaner to do this:

In browser.js

const {x, y, width, height} = this.columnContainer.getBoundingClientRect()

delta.deltaX = x
this.roiManager.renderSVGContext(context, delta)

and in ROIManager.js the calls to fillRect look like this:

renderSVGContext(context, {deltaX, deltaY}) {


    context.fillRect(x-deltaX, y+deltaY, width, height)
    
    
    context.fillRect(xx-deltaX, yy+deltaY, ww, hh)
}

[wilsonGen]

@turner Oh right, this is much cleaner, thank you for the suggestions.

[jrobinso]

@wilsonGen Thanks for the fix