Add qDecodeDataUrl overload for QString, Q*StringView or such-like

Qt has a private function to parse data from base64 encoded strings. It takes a QUrl as a parameter, which in some cases has to be constructed from a string, e.g. in QSvgHandler, only to be converted back within the function.

Suggested solution: Overload bool qDecodeDataUrl(const QUrl &url, ...); with options so QString and similar classes can be passed efficiently.