Maintaining big list

[taoky]

现有的 big list 硬编码了下面的 URL：

big = {
    'centos': '/7/isos/x86_64/CentOS-7-x86_64-Everything-2009.iso',
    'centos-vault': '/6.0/isos/x86_64/CentOS-6.0-x86_64-LiveDVD.iso',
    'opensuse': '/distribution/leap/15.5/iso/openSUSE-Leap-15.5-DVD-x86_64-Media.iso',
    'ubuntu-releases': '/22.04/ubuntu-22.04.3-desktop-amd64.iso',
    'debian-cd': '/current/amd64/iso-bd/debian-edu-12.1.0-amd64-BD-1.iso',
    'kali-images': '/kali-2023.2/kali-linux-2023.2-live-amd64.iso',
    'CTAN': '/systems/texlive/Images/texlive.iso',
    'blackarch': '/iso/blackarch-linux-full-2023.04.01-x86_64.iso',
    'archlinux': '/iso/latest/archlinux-x86_64.iso',
    'ubuntu': '/indices/md5sums.gz',
    'debian': '/ls-lR.gz',
}

其中有一些目录要定时更换，需要考虑怎么做更合适。