vendor: update Snap.svg to latest head
draw: pass in svg element to Snap constructor

Fix for running Snap under a shadow root
vendor: add pointerevents
add PointerEvents polyfill
Revert "add PointerEvents polyfill"

This reverts commit c3d39d05bd19ce3154569d57c53c3b73557a2510.
draw: clear out innerHTML for new Drawing