More granular viewport configuration

[bradfrost]

This is a feature request from someone at a company. They'd like to have more control over the ish controls. Rather than selecting ranges, they'd like to do something like:

• iPhone - exactly 320
• Android - exactly 360
• iPad - exactly 768
• L - 768 to 1200
• XL - 1200 to 1800
• Jumbo - 1800 to 3000

You get the idea. I'm not sure what the default ish configurations are, but this was presented to me.

[bmuenzenmeyer]

release https://github.com/pattern-lab/styleguidekit-assets-default/releases/tag/v3.5.0 allows users to specify a viewport range for the default S, M, L buttons, including defining an exact size for each.

This doesnt allow users to create more than three, however.