extract.py - download all articles locally by running a script

[alikatgh]

Download all articles by running a script included in directory

[facundoolano]

Hi Albert, thanks for the PR. I will have to decline it though, since it doesn't match a few goals I have for this repository:

1. I don't know what the copyright/permissions situation is for most of the papers, I imagine that, at least for some of them, you can't just copy them and serve them into a repository without getting permissions. That's why I went with just storing a link to the paper.
2. Keeping a local copy adds overhead to the the maintenance of the list, which changes frequently. I prefer to just have a spec in the yaml. I also don't want to maintain the script that downloads the papers (and especially not one that requires human input to work). You'll see that there's a script to check the articles are online, and even in that case I have plans to remove it and use a standard github action instead.

I understand it's inconvenient when links go down. It's usually easy to find a replacement link, what I'm missing is to update that link checking script to run on a schedule (e.g. everyday) so I find out when a link goes down. That should solve most of the problem.