Link caniuse feature for Lab and LCH (#1192)

Author: foolip

features/lab.yml

@@ -1,6 +1,7 @@
 name: Lab and LCH
 description: "The CIE Lab color space expresses colors in terms of lightness and how red/green and blue/yellow a color is. LCH is a variant of Lab with polar coordinates. These color spaces can be used with the CSS `color()`, `lab()`, and `lch()` functions. Also known as CIELAB and CIELCH."
 spec: https://drafts.csswg.org/css-color-4/#cie-lab
+caniuse: css-lch-lab
 # Editorial override has been applied to ignore mixed_type_parameters.
 # TODO: The behavior of lightness gradients requiring gamut mapping is a
 # topic of debate, and at least these browser bugs: