capture the css blocks, great to use with sheet.insertRule

get-block-css.ts

const add = (list: string[]) => (rule: string) => list.push(rule) && "";
function parse(css: string) {
  const rules = [];
  const atRules = [];

  css
    .replace(/\s+/g, " ")
    .replace(/@([^{]+)\{(.*?}) *}/g, add(atRules))
    .replace(/([^}{;]*){([^}{]+)}/g, add(rules));

  return [...rules, ...atRules];
}