Zoomable MerzView

[ryanbugden]

Also sort of a nice-to-have. So the user can fit more text in view, or see any elements that might be cropped off.

Thinking started here:

underlineStrikethrough/Underline Strikethrough.roboFontExt/lib/Underline StrikeThrough.py

Line 209 in 67c2839

# def magnifyWithEvent(self, sender, event):