fix(http): set headers on resposne manually (#1526)

The browser `Response` constructor removes `set-cookie` headers and so we set them manually.

closes #1470

Author: amrbashir

.changes/http-set-cookie.md

@@ -0,0 +1,5 @@
+---
+"http-js": "patch"
+---
+
+Fix missing `Set-Cookie` headers in the response which meant `request.headers.getSetCookie()` always returned empty array.

plugins/http/api-iife.js

@@ -209,8 +209,16 @@ export async function fetch(
     },
   );
 
-  // url is read only but seems like we can do this
+  // url and headers are read only properties
+  // but seems like we can set them like this
+  //
+  // we define theme like this, because using `Response`
+  // constructor, it removes url and some headers
+  // like `set-cookie` headers
   Object.defineProperty(res, "url", { value: url });
+  Object.defineProperty(res, "headers", {
+    value: new Headers(responseHeaders),
+  });
 
   return res;
 }