add link to new-machine-cymru in howto index

howto.md

@@ -14,6 +14,7 @@ various procedures not necessarily associated with a specific service.
  * [lektor](howto/lektor)
  * [lvm](howto/lvm)
  * [new-machine](howto/new-machine)
+ * [new-machine-cymru](howto/new-machine-cymru)
  * [new-machine-hetzner-cloud](howto/new-machine-hetzner-cloud)
  * [new-machine-hetzner-robot](howto/new-machine-hetzner-robot)
  * [new-machine-mandos](howto/new-machine-mandos)