Move config files to XDG-compatible path

Move config files to XDG-compatible path: `$HOME/.config/emacs`.

.config/emacs/config/backups.el

@@ -1,5 +1,5 @@
 ;; configure backups
-(setq backup-directory-alist '(("." . "~/.emacs.d/backups/")
+(setq backup-directory-alist '(("." . "~/.config/emacs/backups/")
                                ("/dev/shm" . "/dev/null"))
       backup-by-copying t
       delete-old-versions t

.config/emacs/init.el

@@ -40,7 +40,7 @@
 (require 'use-package)
 
 ;; file used for storing customization information
-(setq custom-file "~/.emacs.d/custom.el")
+(setq custom-file "~/.config/emacs/custom.el")
 (load custom-file)
 
 ;; set auth-sources
@@ -61,7 +61,7 @@ symbols, which are converted to strings, and suffixed with \".el\"."
   :group 'config-snippets
   :type '(repeat (choice symbol string)))
 
-(defcustom config-snippet-path '("~/.emacs.d/config/")
+(defcustom config-snippet-path '("~/.config/emacs/config/")
   "Specifies the path in which config snippets are searched"
   :group 'config-snippets
   :type '(repeat directory))