Add Docker course playlist by Robert Silva to `free-courses-pt_BR.md` (#7081)

* Update free-courses-pt_BR.md

* Update courses/free-courses-pt_BR.md

Co-authored-by: ImVector <59611597+LuigiImVector@users.noreply.github.com>

Co-authored-by: ImVector <59611597+LuigiImVector@users.noreply.github.com>

courses/free-courses-pt_BR.md

@@ -7,6 +7,7 @@
 * [Dart](#dart)
 * [Database](#database)
 * [Delphi](#delphi)
+* [Docker](#docker)
 * [Flutter](#flutter)
 * [Git](#git)
 * [Go](#go)
@@ -87,6 +88,11 @@
 * [Aprenda Delphi e Lazarus do Zero - 100% Gratuito](https://www.udemy.com/aprenda-delphi-e-lazarus-do-zero/) - Marcos Fabricio Rosa (Udemy)
 
 
+### Docker
+
+* [Curso de Docker Completo](https://www.youtube.com/playlist?list=PLg7nVxv7fa6dxsV1ftKI8FAm4YD6iZuI4) - Robert Silva (YouTube)
+
+
 ### Flutter
 
 * [Criando seu primeiro App com Flutter](https://app.balta.io/courses/7184) - Andre Baltieri (balta.io)