Optimize get page scrollheight

in some cases the default document.body.scrollHeight is not sufficient, there can be other factors that influence determining the height of the page
for full page screenshots the scollbars only need to be hidden after a scroll, bot before. This might block scrolling in some situations
in some cases the scroll can't be done on the window, it need to be done on the largest element.
add tests and increase coverage
fix to add overflow to the body instead of the html element
update dependencies

wswebcreation / webdriver-image-comparison