Add Bash courses (#2927)

free-courses-pl.md

@@ -1,6 +1,7 @@
 ### Index
 
 * [Assembly Language](#assembly-language)
+* [Bash](#bash)
 * [Brainfuck](#brainfuck)
 * [C](#c)
 * [C#](#c-sharp)
@@ -19,6 +20,12 @@
 * [Gynvael's Asm (PL)](https://www.youtube.com/playlist?list=PL7CA8FE35B665D4DD) - Gynvael Coldwind
 
 
+### Bash
+
+* [Bash - Skrypty powłoki](https://www.youtube.com/playlist?list=PLh6V3IQZSBSbls0j9DdkCpbbqQsBUzh4-) - Piotr Kośka
+* [Kurs BASH](https://www.youtube.com/playlist?list=PLHYqnLVqlfpyHMKNUkkdFQfueRcsssEj0)
+
+
 ### Brainfuck
 
 * [Programowanie w Brainfucku](https://www.youtube.com/watch?v=dzFgY4JsZe8)