fetch works, needs test

lib/server.ts

@@ -190,14 +190,23 @@ export function createApp(devJsonPath: string, opts: DevOptions): Express.Applic
   }
 
   function setupUrlGateway(gatewayUrl: string) {
-    // Setup express to redirect or proxy to a URL gateway
-    app.use((req, res, next) => {
-      if (req.path === "/") {
-        return next();
-      }
-      // Redirect or proxy to the URL
-      res.redirect(gatewayUrl + req.url); // Simple redirect, adjust if you need to proxy
-    });
+    fetch(gatewayUrl)
+      .then((response) => {
+        if (!response.ok) {
+          throw new Error('Failed to fetch gateway content');
+        }
+        return response.text();
+      })
+      .then((data) => {
+        const modifiedDist = handleReplacements(data, opts);
+        app.get("*", (_, res) => {
+          res.send(modifiedDist);
+        });
+      })
+      .catch((err) => {
+        log.error(err);
+        log.error("Failed to set up URL gateway.");
+      });
     log.success("URL gateway setup successfully.");
   }