Add vietnamese translation

Author: hienvd

README.md

@@ -2156,6 +2156,6 @@ This is also available in other languages:
   - ![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)
   - ![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/)
-
+  - ![vi](https://raw.githubusercontent.com/gosquared/flags/master/flags/flags/shiny/24/Vietnam.png) **Vietnamese**: [hienvd/clean-code-javascript/](https://github.com/hienvd/clean-code-javascript/)
 
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