Multiple versions

[karbyshevds]

As a operations engineer I'd like to be able to switch between documentation versions. Documentation page should display latest stable release by default but it's also should be a dropdown or any other selector to change documentation version on the fly. That's common practice that required to simplify work with ODAHU system and make it more friendly.

Documentation is build via sphinx and hosted on github pages currently so there are two main options for now:

1. Use sphinx plugin that allows to generate docs for multiple versions and adds version selector to final result.
   Pros:
   • stay on github pages
     Cons:
   • all documentation should be rebuilt when new version released
   • plugin looks outdated and forks are also seems dead
2. Migrate to readthedocs.org that can keep multiple versions natively
   Pros:
   • do not require changes for documentation build logic & plugins usage
     Cons:
   • migration