Revert "Remove use-package-font-lock-keywords"

This reverts commit 37d8832.

Author: jwiegley

use-package-core.el

@@ -328,6 +328,13 @@ Must be set before loading use-package."
       (set-default sym value))
   :group 'use-package)
 
+(defconst use-package-font-lock-keywords
+  '(("(\\(use-package\\)\\_>[ \t']*\\(\\(?:\\sw\\|\\s_\\)+\\)?"
+     (1 font-lock-keyword-face)
+     (2 font-lock-constant-face nil t))))
+
+(font-lock-add-keywords 'emacs-lisp-mode use-package-font-lock-keywords)
+
 (defcustom use-package-compute-statistics nil
   "If non-nil, compute statistics concerned use-package declarations.
 View the statistical report using `use-package-report'. Note that