Add color-mix() feature (web-platform-dx#527)

Author: foolip

feature-group-definitions/color-mix.yml

@@ -0,0 +1,15 @@
+name: color-mix()
+spec: https://drafts.csswg.org/css-color-5/#color-mix
+status:
+  baseline: low
+  baseline_low_date: 2023-05-09
+  support:
+    chrome: "111"
+    chrome_android: "111"
+    edge: "111"
+    firefox: "113"
+    firefox_android: "113"
+    safari: "16.2"
+    safari_ios: "16.2"
+compat_features:
+  - css.types.color.color-mix