fix(inlineStyles): dont remove wrapper class if traversed

[SethFalco]

Inline Styles would remove the class from a node after inlining the styles. However, this would break vectors if that class was still needed by another vector though traversal.

For example:

<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 45 35">
  <style>
    .a {}

    .c {}

    .a .b {
      fill: none;
      stroke: #000;
    }
  </style>
  <g class="a c">
    <circle class="b" cx="42.97" cy="24.92" r="1.14"/>
    <path class="b" d="M26,31s11.91-1.31,15.86-5.64"/>
  </g>
</svg>

We can inline .a, however, by removing the class="a" on the group, .a .b no longer selects the circle and path nodes.

This preserves that class if it's traversed in another selector. The class c is still removed.

Notes

• Despite adding a dependency on css-what, it's worth noting we already depend on it, as it's a dependency of css-select. This has no impact on the package/bundle size.

Metrics

Tested using preset-default of each respective version.

SVG	time	% reduced	final size	borked
Original			3.395 KiB
v3.0.3	38 ms	47.1%	1.797 KiB	borked
main (7e25b62)	47 ms	47.6%	1.777 KiB	borked
this branch	50 ms	40.4%	2.021 KiB

Related

• Closes SVGO strips styles #1077