Add Polish translation

Author: greg-dev

README.md

@@ -2174,6 +2174,7 @@ This is also available in other languages:
     - [beginor/clean-code-javascript](https://github.com/beginor/clean-code-javascript)
   - ![de](https://raw.githubusercontent.com/gosquared/flags/master/flags/flags/shiny/24/Germany.png) **German**: [marcbruederlin/clean-code-javascript](https://github.com/marcbruederlin/clean-code-javascript)
   - ![kr](https://raw.githubusercontent.com/gosquared/flags/master/flags/flags/shiny/24/South-Korea.png) **Korean**: [qkraudghgh/clean-code-javascript-ko](https://github.com/qkraudghgh/clean-code-javascript-ko)
+  - ![pl](https://raw.githubusercontent.com/gosquared/flags/master/flags/flags/shiny/24/Poland.png) **Polish**: [greg-dev/clean-code-javascript-pl](https://github.com/greg-dev/clean-code-javascript-pl)
   - ![ru](https://raw.githubusercontent.com/gosquared/flags/master/flags/flags/shiny/24/Russia.png) **Russian**:
     - [BoryaMogila/clean-code-javascript-ru/](https://github.com/BoryaMogila/clean-code-javascript-ru/)
     - [maksugr/clean-code-javascript](https://github.com/maksugr/clean-code-javascript)