build example list page
add isVisible helper
(wip) draw view
use translucent navigation bar
don't load image until it is viewed
don't auto set content size
set image on draw view after appearance
add draw image controller
add draw image controller subspec
pass through scroll zoom delegates
cancel strokes on zoom
add stack helper methods
collect draw history
add framework subspec
add undo/redo
add undo/redo to example