Add env-1.vim

https://www.w3.org/TR/2025/WD-css-env-1-20250923/

Author: hail2u

after/syntax/css/env-1.vim

@@ -0,0 +1 @@
+syn region cssFunction contained matchgroup=cssFunctionName start="\<env\s*(" end=")" oneline contains=cssValueInteger,cssValueNumber,cssValueLength,cssFunctionComma

test/test.css

@@ -391,6 +391,10 @@
   display: linear(0, 0.25, 1);
 }
 
+.env-1 {
+  display: env(foo, red, blue);
+}
+
 .exclusions-3 {
   wrap-flow: auto;
   wrap-through: auto;