Fixes LMS-1740 by activating the zooming diagram with the spacebar.

The zooming diagram has some accessibility problems. Diagrams with text like the one in the demo course should probably be vector images that can be zoomed with the browser or OS's native assistive tech.

But one bug that we can fix is activating the loupe using the keyboard. You still need to use the mouse to navigate around the image, though.
@Lyla-Fischer @frrrances