Make team handbook a web page

@sabbap can you make https://docs.google.com/a/gitlab.com/document/d/1YaRZGWCMuPYL3c8M1wknRxyS5352otj_xGc9ws8-nDs/edit#heading=h.7byzvdqkdjgx into a https://about.gitlab.com/team-handbook/ webpage?

Please use ordered list (ol) so we can refer to numbers.