import attributes polyfill

importCss.js

async function importCss(url) {
	try {
		return await (new Function(`return import("${url}", { with: { type: "css" } })`))();
	} catch {
		try {
			return await (new Function(`return import("${url}", { assert: { type: "css" } })`))();
		} catch {
			return fetch(url).then(res => res.text()).then(cssText => {
				const stylesheet = new CSSStyleSheet();
				stylesheet.replaceSync(cssText);
				return { default: stylesheet };
			});
		}
	}
}

// usage:
// const css = await importCss('https://unpkg.com/open-props');
// document.adoptedStyleSheets = [...document.adoptedStyleSheets, css.default];