[FR] add an optional cumulative sum / cumulative percent column

[mayeut]

This might help to get some useful statics for projects when using a specific order column (e.g. libc-version, pyversion, ...)

The idea comes from mayeut/manylinux-timeline#529 (comment)

[hugovk]

I've written a little helper script to achieve this sort of thing before:

https://discuss.python.org/t/moving-packaging-and-installers-to-macos-10-13-as-a-minimum/31907/5

Sounds like a good idea to have it built-in.

Would you like to work on a PR?