Change default quality for JPEG (and WEBP) from 60 to 80

[mosbth]

Currently the default quality setting for JPEG images are 60.

WEBP images will be using the same &quality and GD uses 80 as default quality when creating WEBP images.

JPEG with quality 60 is a bit low, so changing the default quality to 80, for both JPEG and WEBP, seems like a proper way to go.

Or, perhaps have two different settings of default quality, one for JPEG and one for WEBP. Lets see...

One can always override this by setting another value for default quality in the config file.