add docs for recently-merged -version option for hyperv

website/source/docs/builders/hyperv-iso.html.md.erb

@@ -94,6 +94,9 @@ builder.
     Packer to wait for 1 minute 30 seconds before typing the boot command.
     The default duration is "10s" (10 seconds).
 
+-   `configuration_version` - This allows you to set the vm version when
+     calling New-VM to generate the vm.
+
 -   `cpu` (number) - The number of CPUs the virtual machine should use. If
     this isn't specified, the default is 1 CPU.
 

website/source/docs/builders/hyperv-vmcx.html.md.erb

@@ -125,6 +125,9 @@ builder.
     Where $copy is replaced with either true or false depending on the value of
     "copy_in_compare".
 
+-   `configuration_version` - This allows you to set the vm version when
+     calling New-VM to generate the vm.
+
 -   `cpu` (number) - The number of CPUs the virtual machine should use. If
     this isn't specified, the default is 1 CPU.