Works very well for me.

dieulot, is there a small bug with the allowQueryString check?

    const allowQueryString = 'instantAllowQueryString' in document.body.dataset

I think should be:

    const allowQueryString = 'instantallowquerystring' in document.body.dataset

If I have:

    <body  data-instantAllowQueryString="foo">

then

    'instantAllowQueryString' in document.body.dataset === false

and

    'instantallowquerystring' in document.body.dataset === true

because html data attributes get converted to lowercase by the browser (I think).