Add Georgian (kartuli ena) language translation

[rakvium]

• add ka.yml locale file to config/locales
• copy https://github.com/rakvium/blog/blob/master/config/locales/en.yml content into it
• replace en: with ka: in ka.yml
• replace English translations with Georgian ones in ka.yml
• add ka into array of available locales in https://github.com/rakvium/blog/blob/master/config/application.rb
• submit a pull request with your changes
• get the tests pass

Notice: language_name translation is for Georgian language name in Georgian

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More on localization for Ruby on Rails: https://guides.rubyonrails.org/i18n.html
Key words: Georgian, i18n, internationalization, ქართული ენა, Kartvelian, localization, Sakartvelo