set minimum version to terraform 0.13 (#13)

Author: hyder

versions.tf

@@ -0,0 +1,11 @@
+terraform {
+  required_providers {
+    oci = {
+      source = "hashicorp/oci"
+    }
+    template = {
+      source = "hashicorp/template"
+    }
+  }
+  required_version = ">= 0.13"
+}