[G6] Add manual override for reduce motion.

[prplwtf]

Is your feature request related to a problem? Please describe. Firefox and Waterfox currently only allow a manual override of enabling reduced motion, not disabling it. Reduced motion hinders website development by altering CSS styles for elements, specifically animations. This option defaults to the system preference, which in my and many other cases, is implemented poorly by the window manager or is inside of one of many hidden ~/.config/ configurations.

Describe the solution you'd like An about:config or settings menu override for disabling/enabling reduced motion manually, instead of relying on desktop preferences served by the window manager.

Describe alternatives you've considered Chromium.

Additional context The current configuration value is called "ui.prefersReducedMotion", which is a number with either the value one or zero.

• "1": Enables reduced motion.
• "0": Does not disable reduced motion, this value defaults reduced motion to the OS standard, which this feature request is about.