loongson/pypi: links for chemstruct

loongson/mirror chemstruct-2019.6.2.tar.gz
loongson/mirror chemstruct-2019.6.2-py3-none-any.whl
loongson/mirror chemstruct-2019.6.1.tar.gz
loongson/mirror chemstruct-2019.6.1-py3-none-any.whl