[tldoc] tl2021 manual translations

[Karl Berry]

Hi Ky-Anh,

    $ touch examples/{ex5,ex6a}.tex

All those files are in texlive-common/examples, where texlive-common is
a sibling directory to texlive-en (and all the other texlive-??
directories). What we do is set 
  TEXINPUTS=.:../texlive-common:../texlive-en:; export TEXINPUTS

before running TeX (e.g., in texlive-en/Makefile) so that those
directories are searched automatically. (texlive-en would only be needed
if the default tex-live.sty or live4ht.cfg are used.)

Hope this helps,
Karl