Redesign zoom controls

[jwzimmer-zz]

When I view the editor in Chrome's default zoom, the editor's zoom controls are outside of the visible part of the screen, and there's no obvious scroll or any other indication that there is functionality outside of my view.

[fsih]

I think this is alleviated for now since @mewtaylor reduced the size of the editing area of the paint editor.
But in the longer term, should we change the zoom button design @carljbowman ? Maybe copy the blocks workspace zoom controls?

[carljbowman]

@fsih - I agree, longer term we need a better solution. Reusing the zoom controls from the blocks workspace is a good call. Having the controls fixed to the bottom left corner of the canvas will certainly help with the smaller screen size. 👍

Although evening longer term, we may need to think of ways of adjusting the canvas size vertically within shorter screens.

[fsih]

Moving this to backlog so we can schedule a time later to redesign zoom controls, which I think should go with making the canvas fill the available space