emacs: add Sass support

modules/emacs/.doom.d/packages.el

@@ -56,3 +56,8 @@
    :files ("org-fragtog.el")))
 
 (package! ox-hugo)
+
+(package! sass-mode :recipe
+  (:host github
+   :repo "nex3/sass-mode"
+   :files ("sass-mode.el")))