Make use of scale factor

[martinfleis]

Some providers in xyzservices have an option to pass a scale factor {r}. We may try to expose it in contextily to get a higher DPI when needed.

[yargk]

This would be great. I'm new to contextily and it's hard for me to understand why the dpi doesn't increase when I increase the zoom and use more tiles. The names of places do get smaller, but they are no less fuzzy and the geographic features aren't less fuzzy either. Why is this, more tiles should mean more pixels, right? Besides this, literally every example I see online that uses contextily features basemaps that are not sharp. Does it ever look sharp?