Add Font Hinting Preference and Font weight support in QSS

Qt supports Font Hinting attribute for fonts, which makes text much smoother on Windows platform. Unfortunately, there is no way to set this attribute through QSS.

Similarly, there are variable weight fonts now, which support multiple font weights, that can also only be specified using QFont::Weight enum programmatically.

It would really be helpful if support is added in QSS to set font weight and hinting preference. so UI can easily be customized on per-widget basis e.g. in my case I need would like to use hinting for specific labels and different weights as well.