Update ruby-1.vim

https://www.w3.org/TR/2021/WD-css-ruby-1-20211202/

after/syntax/css/ruby-1.vim

@@ -1,3 +1,4 @@
 syn match cssFontProp contained "\<ruby-\(position\|merge\|align\|overhang\)"
+syn keyword cssFontAttr contained merge
 syn match cssFontAttr contained "\<ruby-\(base\|text\)-container\>"
 syn match cssFontAttr contained "\<inter-character\>"

test/test.css

@@ -752,6 +752,7 @@ mask {
 	ruby-overhang: auto;
 	display: ruby-base-container;
 	display: ruby-text-container;
+	display: merge;
 	display: inter-character;
 }