Improve experience when the frame overflows the available space

[Inwerpsel]

Currently, if you zoom in enough, or use a large screen size, the frame will extend under the right sidebar and/or the bottom of the screen.

If an element is then scrolled into view, it can also make the frame go under the left sidebar.

While this behavior is not that bad, it results in some problems and needs some extra elements to be usable.

• There is no indication of where you zoomed in or how much was cut off from any of the sides. This could be shown in the full height frame, though sometimes it's too small if the page is really long.
• The user cannot move the frame in the same way the browser does when scrolling an element into view.
• Because the scale is done using a transform, the browser is not consistently able to put the element actually into view or in the intended position.

Possible improvements:

• Perhaps simply making X axis scrollable works well. Probably tricky because a transform is used.
• If native scrollbars prove challenging, it might be overall easier to make an own implementation for this purpose.