Vietnamese Translation

I've translated the messages.json file from English to Vietnamese.
The files is located in src/_locales/vi/messages.json

Some has not been translated because I'm aware that Google Chrome uses it to recognize the extension and I also want to keep the originality of the extension names.

ExtName, ExtShortName and ExtDescription->description are not translated.

This is my first ever GitHub contribution so I hope you like it! :)