Word count in extension icon to signal progres [feature request]

[senpl]

It is sometimes useful to know at which point of text we are currently and how long reading will take. So simple word count to end of current speaked selection would be nice. SpeakIt (https://chrome.google.com/webstore/detail/speakit/pgeolalilifpodheeocdmbhehgnkkbak) already do something like that.