CSS Custom Properties not supported #89
Description
CSS Custom properties are ignored as are the rules which use them.
const
cssstyle = require('cssstyle'),
customProp = new cssstyle.CSSStyleDeclaration(),
normalProp = new cssstyle.CSSStyleDeclaration();
customProp.cssText = `--hello-world: blue; background: var(--hello-world);`
console.log(customProp.background) // "" -- ❌ expected "blue"
normalProp.cssText = `background: blue;`
console.log(normalProp.background) // "blue" -- ✅Unlike the CSS color names PR, I have no idea how to resolve this issue.
I don't mind contributing to solve this issue, but I will likely need some help.