Method lunch

mod.rs:20–26

(topping: &str)

    // Implement functionality for the Pizza struct
    impl Pizza {
        pub fn lunch(topping: &str) -> Pizza {
            Pizza {
                dough: String::from("regular dough"),
                cheese: String::from("mozzarella"),
                topping: String::from(topping),
            }
        }
    }

    // help_customer is public so functions can call it