Userscript version of "Google Translate This" from https://github.com/andreicristianpetcu/google_translate_this. v0.1 2019-11-03
As of 2019-11-03 21:19:55 UTC. See the latest version.
Userscript implementation because extensions cannot inject remotely hosted scripts like Google's Translate widget script.
To inject the widget, use the Violentmonkey or Tampermonkey menu. If there is a way to do it in Greasemonkey, let me know.
Version 0.1 does not let you specify sites where you want the widget injected automatically, but maybe someone will build that.