Have a bio space for contributors

[swfsql]

There is a resourceful infographics scheme on overleaft: https://www.overleaf.com/latex/templates/infographics-cv/hdgkztmhztph

Contributors should have a space where they can define their bio, to serve as a small CV to be added as a backmatter of the book, along with the author's information and forward links.

The bio should be one or two small phrases. I'm thinking of letting every contributor to pick one or two single graph resource and then put arbitrary information for it - but the space should be relatively small.
Besides this, offer an option so each one can add their contact information, such as steemit user, email, and so on.

It should be possible to fetch the user's steemit bio automatically, if he has given his steemit user info.
This should make it easier that he doesn't have to keep updating this information on this repo itself.

The contribution on my part will only require that a link for discussion on xx.ancap.ch to be listed on the start and end of the mainmatter, as an annonymous footnote. It doesn't have to be the only nor the first recommended place for discussion and questions.

Moved from ancap-ch/from-en#1629