Similar browser extensions are made before.
HN discussions:
Language Immersion for Chrome
https://news.ycombinator.com/item?id=3921773
Polyglot
HN discussions:
Language Immersion for Chrome
https://news.ycombinator.com/item?id=3921773
Polyglot
"UPDATE: Due to the shutdown of the Google Translate API, Polyglot is no longer being maintained. It's been ported to use Bing Translate but due to rate limits the service is relatively unreliable and cannot be guaranteed to work consistently."