Add ruby config dotfiles for docs

[AndrewSpeed]

Add

• .ruby-gemset to isolate jq docs dependencies from other ruby dependencies installed for other projects, as recommended by the rvm best practices guide
• .ruby-version to automatically have rvm switch to the desired version of ruby automatically when cding into the directory.

[itchyny]

We removed the dependency on Ruby at a4756fd on Feb 27, 2019, so closing.