Adds "Networking" category and IPv6 course (#6068)

* Adds "Networking" category and IPv6 course

Adds "Networking" category and IPv6 course from NIC.br

* Fixes number of blank lines

Fixes number of blank lines

courses/free-courses-pt_BR.md

@@ -25,6 +25,7 @@
 * [Lua](#lua)
 * [Machine Learning](#machine-learning)
 * [Markdown](#markdown)
+* [Networking](#networking)
 * [Node.js](#nodejs)
 * [PHP](#php)
 * [Python](#python)
@@ -206,6 +207,11 @@
 * [Aprenda Markdown](https://www.udemy.com/aprenda-markdown/) - Roberto Achar (Udemy)
 
 
+### Networking
+
+* [Curso de IPv6 Básico a Distância](http://saladeaula.nic.br/courses/course-v1:NIC.br+IPV6-001+T001/about) - NIC.br
+
+
 ### Node.js
 
 * [Criando APIs com NodeJs ](https://www.youtube.com/playlist?list=PLHlHvK2lnJndvvycjBqQAbgEDqXxKLoqn) - Balta.io (YouTube)