chore: add terraform configuration for creating a domain.

Part of #1000

[skip ci]

Author: php-coder

infra/terraform/README.md

@@ -13,6 +13,7 @@
 * Import existing configuration (optionally; only first time)
   ```console
   $ terraform import digitalocean_droplet.web <id>
+  $ terraform import digitalocean_domain.site my-stamps.ru
   ```
 * Plan and apply:
   ```console

infra/terraform/my-stamps.tf

@@ -18,3 +18,7 @@ resource "digitalocean_droplet" "web" {
   private_networking = true
 }
 
+# https://www.terraform.io/docs/providers/do/r/domain.html
+resource "digitalocean_domain" "site" {
+  name = "my-stamps.ru"
+}