Consider adding feature detection for native dynamic import support

[philipwalton]

If the browser natively supports dynamic import, it's better to use that if available. One way to accomplish that would be something like the following:

let importModule;

try {
  importModule = new Function('u', `return import(u)`);
} catch (error) {
  importModule = () => {
    // Existing polyfill logic here...
  }
}

Calling new Function('...') will error with some CSP configurations, but since this is in a try/catch block, if CSP is configured to disallow this, the polyfill fallback will be used. I've tested this myself and it works just fine.