#3522209 Only one viewport

Now there is only one breakpoint shown on the scrollable canvas. You can navigate between viewports with a drop down. A new button centers and scales the preview to fit in your window.

The left side panel can be closed.

The Zoom controls are moved from the bottom to sit at the top center of the preview canvas.

Zooming in and out has been improved (it's still not perfect). There is now a throttle on the zoom in/out that should prevent you from accidentally rapidly scrolling WAY in or WAY out by mistake.

Addressed a bug that meant when zoomed in it was impossible to scroll all the way to the top or bottom of the page you are previewing, the canvas wasn't correctly expanding by enough space so the preview was clipped.