The script used to identify and update the change is added into the GitHub
workflows script directory. A workflow action can be created to trigger the
script to update the headers on the first of every new year. Possibly a task for
a consequent PR.
spacemacs/add-flycheck-hook was not really hooking anything, change the name
to better reflect what it does.
Also changed the push for a add-to-list to avoid duplicates.