Localization struct upgrade

LocalizationStruct.swift

struct Localization {
    let key: LocalizationKey
    let string: String
    
    private init(string: String, key: LocalizationKey) {
        self.string = string
        self.key = key
    }
    
    static func bye(name: String) -> Localization {
        return Localization(string: String(format: LocalizationKey.bye.string, name), key: .bye)
    }
    
    static func hello() -> Localization {
        return Localization(string: LocalizationKey.hello.string, key: .hello)
    }
    
    static func progress(from: Int, to: Int) -> Localization {
        return Localization(string: String(format: LocalizationKey.progress.string, from, to), key: .progress)
    }
}