Update README.md (trekhleb#331)

Adding link to read in portuguese :)

Author: nillswe

src/data-structures/linked-list/README.md

@@ -2,7 +2,8 @@
 
 _Read this in other languages:_
 [_简体中文_](README.zh-CN.md),
-[_Русский_](README.ru-RU.md)
+[_Русский_](README.ru-RU.md),
+[_Português_](README.pt-BR.md)
 
 In computer science, a **linked list** is a linear collection 
 of data elements, in which linear order is not given by