字符串 -> UTF8字符串：
?let imagStr = "https://img.hxdrive.net/uploads/2018/02/20/5a268df93929f33fd5be3ef6a18ced46.10-妻有毒：腹黑大叔寵上天-木瓜 "
let ?imagStr_utf8 =?imagStr.addingPercentEncoding(withAllowedCharacters: CharacterSet.urlQueryAllowed) ?? ""
UTF8字符串 -> 字符串：
let urlStr_utf8 = "https://img.hxdrive.net/uploads/2018/02/20/5a268df93929f33fd5be3ef6a18ced46.10-%E5%A6%BB%E6%9C%89%E6%AF%92%EF%BC%9A%E8%85%B9%E9%BB%91%E5%A4%A7%E5%8F%94%E5%AE%A0%E4%B8%8A%E5%A4%A9-%E6%9C%A8%E7%93%9C"
let urlStr = urlStr_utf8.removingPercentEncoding
