Map light-dark() tests to web-features (#46100)

diff --git a/css/css-color/WEB_FEATURES.yml b/css/css-color/WEB_FEATURES.yml
index 8910dea..cbb0f23 100644
--- a/css/css-color/WEB_FEATURES.yml
+++ b/css/css-color/WEB_FEATURES.yml
@@ -16,6 +16,9 @@
   files:
   - lab-*
   - lch-*
+- name: light-dark
+  files:
+  - light-dark-*
 - name: oklab
   files:
   - oklab-*