Respect prefers-reduced-motion: reduce

[ChasBelov]

Completely disable the functions of nicescroll if the browser reports prefers-reduced-motion is set to reduce

It is an emerging best practice to suppress unsolicited animation if prefers-reduced-motion is set to reduce, indicating that the site visitor has set their operating system to indicate that they don't like animation. This feature is now supported by Chrome, Safari, and Firefox.

Disabling nicescroll automatically in such cases will fall back to the scrolling features of the browser, which generally provide the ability to avoid smooth scrolling.

This is an accessibility issue for people who are sensitive to motion.