Module 3 - adding authentication layer & adding .env reference

Hi @shiffman!

I made an updated version of the weather application for module 3 that makes use of the node environment variables using `.env` and making use of a `config.js` file to take care of things like PORT and USERNAME and PASSWORD for adding a simple authentication layer - similar to using an API key. We can use the version without authentication, but just wanted to bring this to your attention in case this makes sense for you.

See: https://github.com/joeyklee/the-weather-here/tree/with-authentication

Review the current weather application and compare it with the proposed with-authentication version at the linked repository. Start by examining its .env usage and config.js handling of PORT, USERNAME, and PASSWORD. Done would require a maintainer decision on whether this authentication approach belongs in Module 3 and, if accepted, clear integration requirements.

Written by the indexing model from the issue text.