Resize window

[rev]

I tried reducing the size of the configuration window.

new GM_config(
      {
        'id': 'MyConfig',
        ...
        'css': '#MyConfig { width: 30%; height: 30%; }
     }

This results in the `document` inside the `iframe` being resized, but the `iframe` size is unchanged.

I also tried to use a `div` instead of the `iframe`, but that didn't make a difference.

What am I missing?

[rev]

Found an example in https://openuserjs.org/scripts/almaceleste/External_link_newtaber/source

const iframecss = `
    height: 375px;
    width: 435px;
    border: 1px solid;
    border-radius: 3px;
    position: fixed;
    z-index: 9999;
`;

GM_config.open();
GM_config.frame.style = iframecss;