💥 Rename def-package! -> use-package!

Calling this pivotal macro "def-package!" has frequently been a source
of confusion. It is a thin wrapper around use-package, and it should be
obvious that it is so. For this reason, and to match the naming
convention used with other convenience macros/wrappers, it is now
use-package!.

Also changes def-package-hook! -> use-package-hook!

The old macros are now marked obsolete and will be removed when straight
integration is merged.

modules/app/rss/config.el

@@ -19,7 +19,7 @@ easier to scroll through.")
 ;;
 ;; Packages
 
-(def-package! elfeed
+(use-package! elfeed
   :commands elfeed
   :config
   (setq elfeed-search-filter "@2-week-ago "
@@ -64,7 +64,7 @@ easier to scroll through.")
       (kbd "M-RET") #'elfeed-search-browse-url)))
 
 
-(def-package! elfeed-org
+(use-package! elfeed-org
   :when (featurep! +org)
   :after elfeed
   :config