Include how to organize dependencies, middleware, and routes if using the Slim skeleton project

[jbulava]

I noticed the README example includes the dependencies, middleware, and routing all within one file. It may be worth adding a note for anyone using the Slim skeleton project that these should be separated into src/dependencies.php, src/middleware.php, and src/routes.php.

[DavidePastore]

Yes, you're right! Feel free to create a PR for this if you already have something in mind. 👍