OSPP 2021: sync manual translation v1.7 from transfix

[johnnychen94]

@Gnimuc is this all we need to do to update https://docs.juliacn.com/latest/?

Todo:

• [x] bring back CI
  • [x] HTML: #123
  • [x] pdf: #124
• [x] update transifix config .tx

[Gnimuc]

Yeah. Just sync and merge. You could get the preview here: https://juliacn.gitlab.io/JuliaZH.jl/