Refactor core-packages + add gnu-elpa-keyring-update

- Adds melpa-mirror, for those lonely days when melpa is down
- Reduce logging spam from package!
- Revise comments & use outline-mode headings
- Prioritize melpa over elpa

core/packages.el

@@ -41,6 +41,9 @@
 (package! which-key)
 (package! hydra)
 
+;; core-packages.el
+(package! gnu-elpa-keyring-update)
+
 ;; autoload/debug.el
 (package! esup)