fix: map .sss as .css to support sugarss extension

Author: kaisermann

Diff for: src/modules/language.ts

@@ -30,6 +30,7 @@ export const ALIAS_MAP = new Map([
   ['pcss', 'css'],
   ['postcss', 'css'],
   ['sugarss', 'css'],
+  ['sss', 'css'],
   ['sass', 'scss'],
   ['styl', 'stylus'],
   ['js', 'javascript'],