Permissions for dynamically created frames

[TiborUdvari]

Some online editors, such as the p5.js web editor, create dynamic iframes that don't match the URL of the parent, as I tried to explain in #64. The permission change in this PR enables the polyfill in these contexts. Here is the related documentation.

I setup a minimal example with the barebones-ar immersive example [here] to validate it working. (https://editor.p5js.org/TiborUdvari/sketches/zW9qJtK7V).

I thought that having the permission in the script injected by the service worker would be enough, but through some trial and error I found this is the minimal permission change to make it work. For future reference, there is also a match_about_blank permission that might be needed in some cases, although not mine.

Here, it is working in the editor after the changes.