Add CSS files to editorconfig (#19289)

Signed-off-by: lucperkins <[email protected]>

Author: lucperkins

.editorconfig

@@ -5,7 +5,7 @@ charset = utf-8
 max_line_length = 80
 trim_trailing_whitespace = true
 
-[*.{html,js,json,sass,md,mmark,toml,yaml}]
+[*.{css,html,js,json,sass,md,mmark,toml,yaml}]
 indent_style = space
 indent_size = 2