feat: shells/onion Python ecosystem diagram + Scikit-HEP shells

[jpivarski]

This is following up on a Slack conversation with @lukasheinrich and @eduardo-rodrigues about having a common area for shared diagrams. The first of these is the "shells" a.k.a "onion" a.k.a. Jake Vanderplas a.k.a. Scientific Python ecosystem diagram, with the Scikit-HEP version of the same. Namely,

and

We can call this the canonical copy of the diagram, @lukasheinrich can add the pylhe logo, and it should appear in future talks (if speakers can be convinced to take this version of it, rather than one floating around elsewhere).

[eduardo-rodrigues]

Hey @jpivarski, I see you are adding these figures under assets/images/shared-diagrams/shells-onion-jakevdp/. Why not something simpler and more explicit such as assets/images/ecosystem-shells/?

I would also explicitly rename the plots from Jake, so e.g. jakevdp-scipy-shell-1.png, etc. Sounds like a detail but at the moment ours and all his are mixed. Seems confusing if I look at the names.

Anyway, these are mostly content-free comments. Basically cosmetic and personal preferences. Do as you prefer.

[eduardo-rodrigues]

Are you going to add info on these files somewhere on the site? The Scikit-HEP shell figure might actually be really nice somewhere at https://scikit-hep.org/about with some bit of text.

[jpivarski]

The directory originally consisted of all the names I would have thought of to try to find that particular image. I didn't think of "ecosystem shells," but "ecosystem" is going to be a popular search term, given how we talk about it. "Onion" is sometimes used, too, but there's only so much you can do before the name starts looking complicated.

I also included Jake's GitHub user name in the images taken from his original talk, so that the provenance/attribution is there.

I don't have any plans for making these visible on the website itself, though I wouldn't mind if someone does that. This PR is just to get scikit-hep-ecosystem.svg into a shared commons for others to edit, and to establish the convention of doing that.

[eduardo-rodrigues]

Understood Jim. We can certainly add text in some other PR. This is self-contained. Approving AFAIC.