Exposed stack_type variable in compute_vm module (#1756)

* Exposed stack_type variable in compute_vm module

* Updated README.md

* align instance template, fix variable ordering

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Co-authored-by: Ludo <ludomagno@google.com>

modules/compute-vm/variables.tf

@@ -240,15 +240,16 @@ variable "name" {
 variable "network_interfaces" {
   description = "Network interfaces configuration. Use self links for Shared VPC, set addresses to null if not needed."
   type = list(object({
-    nat        = optional(bool, false)
     network    = string
     subnetwork = string
+    alias_ips  = optional(map(string), {})
+    nat        = optional(bool, false)
+    nic_type   = optional(string)
+    stack_type = optional(string)
     addresses = optional(object({
       internal = optional(string)
       external = optional(string)
     }), null)
-    alias_ips = optional(map(string), {})
-    nic_type  = optional(string)
   }))
 }