Enable to reduce/skip css-animation by prefers-reduced-motion media query

The origin of this ticket is to make it possible to skip the CSS-based animations via flag or similar when running tests. See related ticket MGNLTEST-209.

What we are doing here on this ticket on the UI - it is actually seen an an accessibility topic.
See e.g.

• https://developer.mozilla.org/en-US/docs/Web/CSS/@media/prefers-reduced-motion
• https://css-tricks.com/introduction-reduced-motion-media-query/

 Meant for users which may be distracted by too much by animations, etc. pp

The change requested by this ticket for itself will not reduce/skip animations.
It only prepares the ground to run a browser with reduced/skipped animations.
This will be used by chrome-driver when running UI tests.
And it can be used by Magnolia users.