Make the four different quality parameters customizable

Simple change to make quality settings customizable.

Also, wasnt the previous code reversed:

``var quality = (dpr > 1.49) ? 90 : 80;
if (s.webp) quality = dpr > 1.49 ? 65 : 78;``

for webp it it uses a lower quality for high dpr (65) but for non webp it uses the heigher factor (90)