Cross origin

[noam-honig]

In this pull request, we change the code not to use proxy in the dev environment and also prepare it to run on separate API / static servers with different URLs - and support for cors.

We follow the article: How to Set up CORS and Cookie-Session in Express

Here are the main changes we've made.

On the backend

1. We've installed cors

   npm i cors
   npm i @types/cors

2. In index HTML we've adjusted the cookie-session to support calls from different origins and also have two other behaviors - for dev and production
   https://github.com/remult/react-vite-express-starter/compare/completed-tutorial...cross-origin?expand=1#diff-e4e7a68d82cdfba4e7dab9a32a8f55f3806ffa0cf33f1b8ab64b42941cf68888R13-R38
3. We've added cors and specified the valid URLs that can send a request to the server.

On the frontend

1. We've disabled the proxy in the vite.config.ts file.
2. We've added a file with a const API_URL and used it throughout the code.
3. We've added a file called .env.production that will include the URL of the actual server once the app is deployed.
4. We've added `credentials: 'include' to all fetch calls