docs: follow use-package recommendations

use-package documentation recommend to use ':custom' to set variables

Author: roy-corentin

README.md

@@ -43,18 +43,20 @@ common defaults laid out:
 ```emacs-lisp
 (use-package doom-themes
   :ensure t
-  :config
+  :custom
   ;; Global settings (defaults)
-  (setq doom-themes-enable-bold t    ; if nil, bold is universally disabled
-        doom-themes-enable-italic t) ; if nil, italics is universally disabled
+  (doom-themes-enable-bold t)   ; if nil, bold is universally disabled
+  (doom-themes-enable-italic t) ; if nil, italics is universally disabled
+  ;; for treemacs users
+  (doom-themes-treemacs-theme "doom-atom") ; use "doom-colors" for less minimal icon theme
+  :config
   (load-theme 'doom-one t)
 
   ;; Enable flashing mode-line on errors
   (doom-themes-visual-bell-config)
   ;; Enable custom neotree theme (nerd-icons must be installed!)
   (doom-themes-neotree-config)
   ;; or for treemacs users
-  (setq doom-themes-treemacs-theme "doom-atom") ; use "doom-colors" for less minimal icon theme
   (doom-themes-treemacs-config)
   ;; Corrects (and improves) org-mode's native fontification.
   (doom-themes-org-config))