101-firewall-standard patch (#169)

* fix example

* add variable type

quickstart/101-firewall-standard/providers.tf

@@ -0,0 +1,18 @@
+terraform {
+  required_version = ">= 1.0"
+
+  required_providers {
+    azurerm = {
+      source  = "hashicorp/azurerm"
+      version = ">= 3.0, < 4.0"
+    }
+    random = {
+      source  = "hashicorp/random"
+      version = ">= 3.0"
+    }
+  }
+}
+
+provider "azurerm" {
+  features {}
+}