unimplemented functions:

• func Clone(s string) string
• func EqualFold(s, t string) bool
• func FieldsFuncSeq(s string, f func(rune) bool) iter.Seq[string]
• func FieldsSeq(s string) iter.Seq[string]
• func Lines(s string) iter.Seq[string]
• func Map(mapping func(rune) rune, s string) string
• func SplitAfterSeq(s, sep string) iter.Seq[string]
• func SplitSeq(s, sep string) iter.Seq[string]
• func Title(s string) stringdeprecated
• func ToLowerSpecial(c unicode.SpecialCase, s string) string
• func ToTitle(s string) string
• func ToTitleSpecial(c unicode.SpecialCase, s string) string
• func ToUpperSpecial(c unicode.SpecialCase, s string) string
• func ToValidUTF8(s, replacement string) string