[css-snappoints] 3/5 Updated ED

Hi all,

Updates since my last mail include:

Enabling the multiple scroll-snap-coordinate per element scenario via comma-separated list of space-separated pairs (feedback from Seattle f2f)
Eliminating the snap-list and snap-interval functions in favor of a comma-separated list and repeat() syntax (Tab's feedback from Seattle f2f and mail)
Updated grammar notation as specified in CSS Values and Units L3

Thanks,
-Matt