Added support for quality control on WebP image

[isandeepj]

#43
Create a PNG or JPEG image to WebP

We can generate WebP Data following way with quality.
Compares the quality with 60% of WebP image

let image = UIImage(named: "test.png")
guard let data = image.kf.normalized.kf.webpRepresentation(isLossy: true, quality: 60.0) else { return }

Compares the quality with 85% of WebP image

let image = UIImage(named: "test.jpg")
guard let data = image.kf.normalized.kf.webpRepresentation(isLossy: true, quality: 85.0) else { return }

[yeatse]

Thank you for your nice work! I just added some comments. We could merge this PR once they get resolved.

[isandeepj]

@yeatse I have resolved given feedback. Kindly check.

[isandeepj]

@yeatse @dinsen @ShaharHD @guilhermearaujo We are waiting for these changes in the latest version.

[yeatse]

@yeatse @dinsen @ShaharHD @guilhermearaujo We are waiting for these changes in the latest version.

Sorry for my delay 😂 I'm going to merge them now