Add artafinde to dev and multilib groups

group_vars/all/archusers.yml:
Promote artafinde to `dev`.
https://lists.archlinux.org/archives/list/arch-dev@lists.archlinux.org/message/AMAN62A2UERSNWO73G5Y5FRVWBIJNETL/
Also add to `multilib` group (for good measure).

group_vars/all/archusers.yml

@@ -54,6 +54,8 @@ arch_users:
     name: "Leonidas Spyropoulos"
     ssh_key: "artafinde.pub"
     groups:
+      - dev
+      - multilib
       - tu
   anatolik:
     name: "Anatol Pomozov"