CSS Import function. Loads a CSS file relative to the script where the function was called! (like js-module imports)

c1.cssImport.js

c1CssImport = function (location) { // todo: handle absolute urls
    const e = new Error();
    const calledFile = e.stack.split('\n')[2].match(/[a-z]+:[^:]+/);
    const calledUrl = new URL(calledFile);
    calledUrl.search = '';
    const target = new URL(location, calledUrl).toString();
    for (let el of document.querySelectorAll('link[rel=stylesheet]')) {
        if (el.href === target) return; // already loaded
    }
    const link = document.createElement('link');
    link.rel = 'stylesheet';
    link.href = target;
    document.head.append(link);
    // todo: return a promise
}

Ussage:
file: dialog/main.js

c1CssImport('./ui.css'); // loads dialog/main.css if not already loaded
...