Allow activeClass to receive multiple classes

[Francisco Hanna]

As of today, when passing multiple classes to the prop activeClass (i.e. activeClass="font-bold text-blue-500") an exception is thrown:

Uncaught DOMException: Failed to execute 'add' on 'DOMTokenList': The token provided ('font-bold text-blue-500') contains HTML space characters, which are not valid in tokens.

This is because classList.add does not support passing multiple classes separated by a whitespace. To avoid introducing a breaking change (like changing the type of activeClass to receive an array) the string could be splited by whitespaces classList.add(...activeClass.split(' ')).

PS: Great library!