Calculate total css complexity

[bartveneman]

We already support complexity for selectors, but could extend this to add value, property, declaration and atrule complexities. This could also clear the way for having a 'total complexity' for the whole stylesheet.

This would be awesome to graph out as well on projectwallace.com/analyze-css.

Some notes about edge cases and possible scenarios: https://astexplorer.net/#/gist/2d7b3b49ebc7094c0d0b7f29c023b757/ccf6dda1764a26a39098a90842a485916ce3fd4d

Checklist

• Selectors
  • Vendor prefixes
  • Nesting: & .element
• Declarations (basically whether !important is used or not)
• Values
  • Vendor prefixes
  • Browserhacks
• Properties
  • Vendor prefixes
  • Browserhacks
  • Custom properties with and without default values
• @media
  • Browserhacks
• @import
  • media queries
  • layers
  • supports-queries
• @supports
  • Complexity of 'declaration'
  • Vendor prefixes
  • browser hacks
• @container
  • Complexity of 'declaration'
• @keyframes (whether it's vendor prefixed)
• @nest
  • @nest & > .bar -> complexity of & > .bar