add comments in swift code example

Example 1: swift comments

// Use // for comments

/*
Or, you can use this style
*/

Example 2: swift doc comments

/**
     Sign up a new user with email and password
     
     - Parameters:
        - email: email address of user
        - password: new password of user
     
     - Returns: True if the user has successfully signed up, False otherwise
     */
    public func signUp(withEmail email: String, andPassword password: String) -> Bool {
        var complete = false
        auth.createUser(withEmail: email, password: password) { (result, error) in
            if result != nil {
                print(result!.description)
                complete = true
            } else {
                print(error.debugDescription)
            }
        }
        print(complete)
        return complete
    }