feat: Steamify's default setup for the new user during the install (Calamares step before cleanup)

archiso/airootfs/etc/calamares/modules/shellprocess_steamify.conf

@@ -0,0 +1,10 @@
+# Steamify: the Steam Machine setup for the new user, before the first boot.
+---
+
+dontChroot: true
+timeout: 3600
+script:
+    - "-/usr/local/bin/steamify-install ${ROOT} ${USER}"
+
+i18n:
+    name: "Setting up the Steam Machine (Steamify)"