Add infographic

[brian-rose]

This PR introduces the new infographic that summarizes Pythia Foundations and its relation to the cookbooks.

I found that it worked well to repeat the infographic at the beginning of each major section of the book. I made some modest text revisions on each of the relevant pages to accommodate the new graphic and modernize a few things.

This PR also includes a fix for #509

[github-actions]

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[brian-rose]

I tagged a few extra folks for reviews here since this is one the "bigger" more visible content changes we've had in a while.

[jukent]

Looks great! I'm wondering if we want to edit https://foundations.projectpythia.org/_preview/510/landing-page.html as well to include this graphic instead of the glob (which I believe was originally a placeholder).

[brian-rose]

Looks great! I'm wondering if we want to edit https://foundations.projectpythia.org/_preview/510/landing-page.html as well to include this graphic instead of the glob (which I believe was originally a placeholder).

Let's see what others think! Yes, the Earth image was originally a convenient placeholder (#27). It looks nice but doesn't convey any specific information.

[brian-rose]

I'll merge this now and we can discuss the book cover art question separately.