fix: map theme to class using ValueObject in injected script

[danielgavrilov]

I think this is a bug: the CSS classes are being correctly remapped in order to remove them all, but the class being added is not mapped using the ValueObject:

next-themes/next-themes/src/script.ts

Lines 19 to 22 in 57c0561

	const classes = isClass && value ? themes.map(t => value[t] || t) : themes
	if (isClass) {
	el.classList.remove(...classes)
	el.classList.add(theme)