Links to Documentation (pdf)

Currently links to documentation on INSTEAD3 website look like:

• Документация (pdf)
  • http://club.syscall.ru/s/download/stead3.pdf
• Documentation (pdf)
  • http://club.syscall.ru/s/download/stead3.pdf

As stead3.pdf is only in Russian now, then need proper naming for this PDF's as:

• stead3-ru.pdf - for documentation in Russian;
• stead3-en.pdf - for documentation in English.

Also, as this PDF will be attached to releases, then links should look like:

• Документация (pdf)
  • https://github.com/instead-hub/instead/releases/download/3.x.x/stead3-ru.pdf
• Documentation (pdf)
  • https://github.com/instead-hub/instead/releases/download/3.x.x/stead3-en.pdf

Also need same thing for Markdown sources, that used as online documentation.

TODO

• Assets: stead3-ru.pdf, stead3-en.pdf (modules3-ru.pdf, modules3-en.pdf) instead#50

[hugeping]

Currently, there is NO english documentation.
So, i made this hoping someone will translate it.
This is not the bug. When en docs will be created it will be named stead3-en.pdf

This is not the bug.

But lets now use stead3-ru.pdf instead of stead3.pdf for Russian docs.