Add video-like controls to canvas animations

[KaliedaRik]

Issue: Users need to be able to access a mechanism that allows them to play and pause a canvas-based animation. They also need a similar mechanism which will allow them to hide a canvas - particularly for animations that include flickering or flashing content.

See https://www.w3.org/WAI/WCAG21/Understanding/pause-stop-hide.html

[KaliedaRik]

Added new functionality to detect users who set "prefers-reduced-motion" flag to "reduced" in v8.2.4, released 19 Oct 2020.

This functionality allows developers to add functions to their code to slow/stop animations where users have indicated they prefer such an environment. See new demo Canvas-033.

It is for the end developer to decide how they respond to such user preferences, not this library. Will not be developing video-like controls for canvas elements unless someone can come up with a highly compelling use case. No further action required.