Rollup merge of rust-lang#153748 - lolbinarycat:editorconfig-css, r=jieyouxu

editorconfig: css uses tabs

Tidy enforces the fact that css files use tabs, but currently `.editorconfig` says everything that isn't llvm or a Makefile should always use spaces.  This PR makes it so all editors that honor `.editorconfig` will use the correct indentation for css files.

Author: Zalathar

.editorconfig

@@ -12,6 +12,9 @@ trim_trailing_whitespace = true
 indent_style = space
 indent_size = 4
 
+[*.css]
+indent_style = tab
+
 # some tests need trailing whitespace in output snapshots
 [tests/**]
 trim_trailing_whitespace = false