Bring back nlinum

linum-mode *really* slows down buffers when they're displayed in more
than one window. This lag isn't present in nlinum. nlinum isn't perfect
either but... lesser of two evils.

This includes advisors and an ESC hook to mitigate the issue of
disappearing nlinum line numbers.

modules/app/regex/autoload/regex.el

@@ -71,7 +71,7 @@
           (with-current-buffer +regex--expr-buffer
             (conf-mode)
             (rainbow-delimiters-mode +1)
-            (linum-mode -1)
+            (doom/toggle-line-numbers +1)
             (setq-local require-final-newline nil)
             (+regex-mode +1)
             (text-scale-set 3)))
@@ -98,7 +98,7 @@
         (switch-to-buffer (get-buffer-create "*doom-regex-repl*"))
         (conf-mode)
         (rainbow-delimiters-mode +1)
-        (linum-mode -1)
+        (doom/toggle-line-numbers -1)
         (setq-local require-final-newline nil)
         (setq mode-line-format nil
               +regex--expr-replace-buffer (current-buffer))

modules/ui/doom/config.el

@@ -43,6 +43,10 @@
   :config
   (load-theme +doom-theme t)
 
+  ;; nlinum line highlighting
+  (when (featurep 'nlinum)
+    (doom-themes-nlinum-config))
+
   ;; Add file icons to doom-neotree
   (doom-themes-neotree-config)
   (setq doom-neotree-enable-variable-pitch t