add http/3 helper func

ngx.ts

@@ -135,6 +135,20 @@ export const listen = (...extras: string[]) =>
     `http2 on`,
   ]);
 
+/**
+ * create http/3 (quic) listen directives (+ supporting alt-svc header).
+ */
+export const http3 = (
+  opts: {
+    /** max age for alt-svc header */ ma?: number;
+  } = {},
+) =>
+  conform([
+    "listen 443 quic reuseport",
+    "listen [::]:443 quic reuseport",
+    `add_header Alt-Svc 'h3=":443"; ma=${opts.ma ?? 86400}'`,
+  ]);
+
 /**
  * create a server_name nginx directive.
  *
@@ -176,5 +190,5 @@ export const letsEncrypt = (
  */
 export default Object.assign(
   (value?: string, children?: LooseConfigNode[]) => ngx(value, children),
-  { NGX_VERSION, listen, letsEncrypt, serverName },
+  { NGX_VERSION, listen, letsEncrypt, serverName, http3 },
 );