Stream sink should not be wrapped by colorama on Windows if not stdout / stderr

[Delgan]

Considering a class with isatty() returning True, Loguru's should_wrap() function will return True on Windows, resulting in AttributeError: 'CustomSink' object has no attribute 'flush' when colorama will write to the sink.

class CustomSink:

    def isatty(self):
        return True

    def write(self, message):
        pass

logger.add(CustomSink(), colorize=True) 
logger.info("Boom")

The stream should only be wrapped if equals to sys.__stdout__ or sys.__stderr__. If for some reason another stream needs to be wrapped, user should wrap it himself (in practice, this is probably never needed).