Add compat key for CSS if() (#3144)

Author: foolip

features/if.yml

@@ -2,4 +2,5 @@ name: if()
 description: The `if()` CSS function is an inline conditional value that returns a value based on a set of conditions.
 spec: https://drafts.csswg.org/css-values-5/#if-notation
 group: css
-# No compat keys yet, this feature is planned to ship with Chromium M136
+compat_features:
+  - css.types.if

features/if.yml.dist

@@ -3,4 +3,9 @@
 
 status:
   baseline: false
-  support: {}
+  support:
+    chrome: "137"
+    chrome_android: "137"
+    edge: "137"
+compat_features:
+  - css.types.if