loongson/pypi: links for pyqtwebengine

loongson/pypi PyQtWebEngine-5.15.6.tar.gz
loongson/pypi PyQtWebEngine-5.15.6-cp39-abi3-linux_loongarch64.whl
loongson/pypi PyQtWebEngine-5.15.6-cp37-abi3-linux_loongarch64.whl