V1 for fluid space variables

[mhewson]

Description

This update provides some support for cdr-space-scale-(N) fluid space
these values seek to mimic were possible the values provided in our spacing design foundation
values were calculated via:
https://utopia.fyi/space/calculator/?c=320,16,1.2,1232,20,1.25,7,1,&s=0.75%7C0.5%7C0.25%7C0.2%7C0.15%7C0.25%7C0.2,1.5%7C2%7C3%7C4%7C6,s-l&g=s,l,xl,12
that URL can also be used to extend or modify future spacing values

...

Checklist:

Design:

• Reviewed with designer and meets expectations

Cross-browser testing:

• Chrome
• Firefox
• Edge
• Safari
• iOS
• Android

Unit testing:

• Sufficient unit test coverage (see unit test best practices for ideas)
• Snapshot updates are explained with comment and reference the relevant source code change

A11y:

• Meets WCAG AA standards

Documentation:

• API docs created/updated
• Examples created/updated