fallbackToNetwork does not work with relative URLs

[Knagis]

when fetch-mock is running with fallbackToNetwork = true, any relative URLs are always prepended with /

fetch("image.png") results in network request to "/image.png", when the index.html is not hosted on the root of the domain.

This is because of normalizeURL rebases the URL not to the current pathname:

	} else {
		const u = new URL(url, 'http://dummy');
		return u.pathname + u.search;
	}

[Knagis]

One potential workaround for this could be

new URL(url, typeof location === "undefined" ? 'http://dummy' : location.href);