Dynamically added iframes are not monetized

[sidvishnoi]

1. Visit a non-monetized website.
2. Run following script in console:

      setTimeout(() => {
        const iframe = document.createElement('iframe');
        iframe.src = 'https://sidvishnoi.com/test/wm';
        iframe.allow = 'monetization';
        document.body.append(iframe);
      }, 3000);

Site does not become monetized 3 seconds later. But if same iframe is added before extension runs, site is monetized. I expect iframes often to be injected via scripts, so this (monitoring iframes added) should be supported.

Found when adding E2E tests with iframes - testing with playground not possible without this.