Napkin community material

This is more like promotion or documentation than an issue, but I have nowhere else to post it. Me and my friends started writing human-readable solutions and formal proofs written in lean4 for all of Napkin’s examples and problems. - Napkin solutions: https://napkin-community.github.io/solutions/ (written in Typst) - Source code: https://github.com/napkin-community/solutions - (There are more unorganized solutions at https://i.hyeon.me/napkin-archive, and I plan to organize them and move them.) - Napkin formal proofs: https://github.com/simnalamburt/lean-practice/ I hope interested people join in and once it matures it could be included as a link in the book. :) Thanks!