Move spacing to its own variable in the default config

[sebastiandedeyne]

I generally want the same values available for paddings, margins and negative margins. The defaults seem to be the same too, so I think it makes sense to do this.

• Pros: easier to add new spacing values
• Cons: none that I can think of

[hacknug]

This is something I have on my default config file for every project and I'd love to see this merged. Imho padding and negativeMargin should also use Object.assign() by default using an empty object (just to make it easier for everyone to understand what's going on).

Something else that could also be introduced is a sizing object with common values for width and height:

const sizing = {
  'auto': 'auto',
  'px': '1px',
  '1': '0.25rem',
  '2': '0.5rem',
  '3': '0.75rem',
  '4': '1rem',
  '5': '1.25rem',
  '6': '1.5rem',
  '8': '2rem',
  '10': '2.5rem',
  '12': '3rem',
  '16': '4rem',
  '24': '6rem',
  '32': '8rem',
  '48': '12rem',
  '64': '16rem',
}

[florianbouvot]

I think moving spacing and sizing is a good idea.

What about spaces and sizes for naming ?

[adamwathan]

Made this change for the updated config format in #661 and #662 👍 Using spacing for both the sizing and spacing scale as I think it makes sense for them to be linked.