allow the basic example to pass packer validate
allow the basic example to pass packer validate

tested with Packer v1.3.4.  Without the builders section is complains for " Unknown root level key in template:  " for every key in the JSON.
rnaveiras/packer,dave2/packer,bryson/packer,ricardclau/packer,ricardclau/packer,hashicorp/packer,tas50/packer,dave2/packer,paulmey/packer,pecigonzalo/packer,rnaveiras/packer,timsutton/packer,rnaveiras/packer,rnaveiras/packer,bryson/packer,bryson/packer,grubernaut/packer,dave2/packer,mitchellh/packer,paulmey/packer,dave2/packer,mitchellh/packer,ricardclau/packer,bryson/packer,timsutton/packer,grubernaut/packer,mitchellh/packer,pecigonzalo/packer,ricardclau/packer,bryson/packer,timsutton/packer,timsutton/packer,paulmey/packer,rnaveiras/packer,timsutton/packer,hashicorp/packer,tas50/packer,dave2/packer,paulmey/packer,bryson/packer,tas50/packer,tas50/packer,pecigonzalo/packer,paulmey/packer,grubernaut/packer,rnaveiras/packer,grubernaut/packer,tas50/packer,hashicorp/packer,mitchellh/packer,grubernaut/packer,dave2/packer,tas50/packer,pecigonzalo/packer,mitchellh/packer,ricardclau/packer,hashicorp/packer,grubernaut/packer,timsutton/packer,ricardclau/packer,paulmey/packer