simplify new URL() to use localhost as host as we only check pathname (#3265)

Author: Mpdreamz

preview/preview.js

@@ -188,12 +188,8 @@ const checkRedirects = async (core, path) => {
 
 module.exports = Core => {
   const server = http.createServer((request, response) => {
-    let host = process.env.HOST;
-    if (host == null || host === "") {
-      host = "localhost";
-    }
-
-    const parsedUrl = new URL(`http://${host}${request.url}`);
+    //hardcode to 'localhost' only pathname is checked on parsedUrl
+    const parsedUrl = new URL(`http://localhost${request.url}`);
     const prefix = hostPrefix(request.headers['host']);
     const core = Core(prefix);
     requestHandler(core, parsedUrl, response)