Add option to disable ipv6 (#1951)

* add option to disable ipv6

* don't add ipv6 address

* update docs

src/server/utils/config.ts

@@ -17,6 +17,8 @@ export const WG_ENV = {
   INSECURE: process.env.INSECURE === 'true',
   /** Port the UI is listening on */
   PORT: assertEnv('PORT'),
+  /** If IPv6 should be disabled */
+  DISABLE_IPV6: process.env.DISABLE_IPV6 === 'true',
 };
 
 export const WG_INITIAL_ENV = {