Use port 8080 instead of port 5000

[bryik]

This PR changes the port used by the express server from 5000 to 8080 to avoid "address already in use" error. The quickstart docs should be updated to reflect this, but I'm not sure where they are.

This is what I saw previously (MacOS v12.3.1):

➜  oso-nodejs-quickstart git:(main) npm start

> quickstart@0.0.0 start
> node server.js

node:events:504
      throw er; // Unhandled 'error' event
      ^

Error: listen EADDRINUSE: address already in use :::5000

Apple recently decided to use port 5000 for 'new AirPlay functionality', so anyone who tries to run the quickstart on the latest version of MacOS will likely see this error.

Why change to port 8080 in particular? No reason, this is just the port Svelte changed to when addressing the same issue in their CLI.