add `std::regex` and `std::wregex` simplifications

[slippycheeze]

https://github.com/rizinorg/rz-libdemangle/blob/51d016750e704b27ab8ace23c0f72acabca67018/src/cxx.c#L53

the std::basic_regex type has the same char and wchar aliases that string and iostream-and-co have; consider adding them to your simplification list.