parse_ixbrl should add encoding argument

[fhopecc]

If the encoding of instance is utf8 but the locale encoding is cp950, then it crahsed. Just adding encoding option to specified the encoding of the instance file for parse_ixbrl function as following:

def parse_ixbrl(instance_path: str, cache: HttpCache, instance_url: str or None = None
               ,encoding='utf8'
               ) -> XbrlInstance:

    instance_file = open(instance_path, "r", encoding=encoding)

[manusimidt]

Sounds like a good suggestion. I will implement it in this week.

[fhopecc]

Thanks for adding this function!