- [feature] add four functions:
py
def convert_exif_to_xmp(data: dict, encoding='utf-8') -> dict
def convert_iptc_to_xmp(data: dict, encoding='utf-8') -> dict
def convert_xmp_to_exif(data: dict, encoding='utf-8') -> dict
def convert_xmp_to_iptc(data: dict, encoding='utf-8') -> dict
See the [tutorial](https://github.com/LeoHsiao1/pyexiv2/blob/master/docs/Tutorial.md#convert) for details