loongson/pypi: links for btrfs-backup

loongson/mirror btrfs_backup-0.3.1.tar.gz
loongson/mirror btrfs_backup-0.3.1-py3-none-any.whl
loongson/mirror btrfs_backup-0.3.0.tar.gz
loongson/mirror btrfs_backup-0.2.1.tar.gz
loongson/mirror btrfs_backup-0.2.tar.gz