add server.init() to adapter-vercel

Required since sveltejs/kit#6179, as hooks.js
are initialized in server.init()

Author: SG60

adapter-vercel/files/edge.js

@@ -3,6 +3,10 @@ import { manifest } from 'MANIFEST';
 
 const server = new Server(manifest);
 
+server.init({
+	env: process.env
+});
+
 /**
  * @param {Request} request
  */