Display Hasse diagram for the Subgraph

[vlad902]

Also update the script to generate such graphs.

Closes #183

[vlad902]

I forgot to update the blueprint, will do that now.

[pitmonticone]

Thanks a lot, @vlad902!

leanblueprint pdf returns an error regarding the image we're including.

Please consider running the executable script scripts/run_before_push.sh to avoid this risk.

[vlad902]

Ah, of course. It builds successfully locally, because I have the PNG, but it fails in CI, because I forgot to git add it.