Update free-courses-pt_BR.md (#3321)

free-courses-pt_BR.md

@@ -16,6 +16,7 @@
 * [Java](#java)
 * [JavaScript](#javascript)
 * [Kotlin](#kotlin)
+* [Markdown](#markdown)
 * [Node.js](#nodejs)
 * [PHP](#php)
 * [Python](#python)
@@ -124,6 +125,11 @@
 * [Desenvolvedor Kotlin Iniciante](https://www.udemy.com/desenvolvedor-kotlin-iniciante/) - Gabriel Ferrari, Adriano Sacardo (Udemy)
 
 
+### Markdown
+
+* [Aprenda Markdown](https://www.udemy.com/aprenda-markdown/) - Roberto Achar (Udemy)
+
+
 ### Node.js
 
 * [Criando APIs com NodeJs ](https://www.youtube.com/playlist?list=PLHlHvK2lnJndvvycjBqQAbgEDqXxKLoqn) - Balta.io (YouTube)