loongson/pypi: links for pdfformulas

loongson/mirror pdfformulas-0.0.6-py2.py3-none-any.whl
loongson/mirror pdfformulas-0.0.5.tar.gz
loongson/mirror pdfformulas-0.0.4.tar.gz
loongson/mirror pdfformulas-0.0.3.tar.gz