Add highlight-indentation package

core/core-ui.el

@@ -41,6 +41,13 @@
     "Prevent annoying \"Active processes exist\" query when you quit Emacs."
     (flet ((process-list ())) ad-do-it)))
 
+(use-package highlight-indentation
+  :diminish highlight-indentation-mode
+  :config
+  (add-hook! (prog-mode scss-mode)
+    (unless (eq major-mode 'emacs-lisp-mode)
+      (highlight-indentation-mode 1))))
+
 (use-package nlinum ; line numbers
   :defer t
   :defines nlinum--width