Added Env Loading Functionality.

[Necoo33]

This pr is about for implementing the optional env loading functionality to this liblary. For loading env's, you'll basically write one line of code:

// ...

$router->loadEnv();

// ...

This will scan the document root for all possible variatons of env file names, for example: .env, .env.prod, credentials.env, credentials.env.dev etc.