[Symfony] Add dump-env task

[richardhj]

Add task to run dump-env on deployment

• [ ] Bug fix #…?
• [x] New feature?
• [ ] BC breaks?
• [ ] Tests added?

• [ ] Docs added?

  Please, regenerate docs by running next command: $ php bin/docgen

As recommended on https://symfony.com/doc/current/deployment.html#b-configure-your-environment-variables

Run composer dump-env on every deployment.

The $APP_ENV shall be automatically when using set('dotenv', '{{deploy_path}}/shared/.env.local'); in the deploy.php file.

[richardhj]

Kindly request review from @garak @Tobion