Add Ruby for beginners course (#3178)

* Update free-courses-pt_BR.md

* Update free-courses-pt_BR.md

free-courses-pt_BR.md

 ### Index
 
 * [Git](#git)
+* [Ruby](#ruby)
 
 
 ### Git
 
 * [Git e Github para iniciantes](https://www.udemy.com/git-e-github-para-iniciantes/) - Willian Justen de Vasconcellos (Udemy)
+
+
+### Ruby
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+* [Curso de Ruby on Rails para Iniciantes](https://www.youtube.com/playlist?list=PLe3LRfCs4go-mkvHRMSXEOG-HDbzesyaP) - Jackson Pires (YouTube)