Container coordinates are not recalculated when scroll changes

[yfandino]

If the viewer is not in full size mode, and the highlight selection has been started. If you scroll down the page and try to make another highlight selection, the coordinates are incorrect (The highlight area is rendered in another position).

This is because the containerCoords function in MouseSelection.js gets the coordinates only at the start of the selection.

This could be solved getting the container bounding rect every time.

const containerCoords = (pageX, pageY) => {
    containerBoundingRect = container.getBoundingClientRect();

    return {
      x: pageX - containerBoundingRect.left + container.scrollLeft,
      y: pageY - containerBoundingRect.top + container.scrollTop - window.scrollY
    };
};