Add an editor/contributor section in xrpl.org docs/materials

[wojake]

Must read: XRPLF/xrpl-dev-portal#1264

I believe that there's room for improvement on all pages @ xrpl.org by facilitating a 'Edited by' widget. This may encourage people to contribute to the xrpl.org repo, giving them exposure and such. Some pages may be outdated as the ecosystem adopts better implementation/tech.

I'm not familiar with front-end/webdev, so please submit an official proposal (PR) on behalf of this discussion if consensus is positively met 😄 ! Thank you.

I personally think $2000 is enough for this bounty, but I'm not familiar with webdev. I won't be pursuing this bounty.