Consider adding support for scaleX, scaleY and transform-origin

[rlefevre]

I believe these functions would be supported in all major browsers since IE10 and make sense because there is already scale and rotate.

• https://developer.mozilla.org/fr/docs/Web/CSS/transform-function/scaleX
• https://developer.mozilla.org/fr/docs/Web/CSS/transform-function/scaleY
• https://developer.mozilla.org/fr/docs/Web/CSS/transform-origin

For example, scaleX with transform-origin: left can be used for a progress bar.

Note: scaleZ could also be considered.