customize: Add script

Deleting the initial password for `root` so we can log in to the serial
console for debugging.

Enabling _wpa_supplicant_ to connect to WiFi automatically.

customize.sh

@@ -0,0 +1,6 @@
+#!/bin/sh
+# vim: set sw=4 ts=4 sts=4 et :
+
+passwd -R /mnt/gentoo -d root
+
+systemctl --root=/mnt/gentoo enable wpa_supplicant@wlan0