Multiplayer game as an extension?

This is sad if there is no work around. In this thread:
t/question-about-types-of-inputs-for-extensions/11755/5
It says: “When a viewer clicks into an extension, Twitch sends focus back to the player, to ensure that keyboard shortcuts for the player continue to work. However, if an extension asks viewers to click on a form field element (for example, “field,” “select,” “textarea”), and the viewer does so, the focus stays on the form element.” so I take it there are multiple forms of text input fields?
If there is a way that the user of the extension can click a text box, and have that text box submit their keypresses as they happen rather than when they press enter, then it would be possible to make a game that uses keyboard inputs until the time when the viewer clicks out of the text box with his mouse.
So it would be either mouse only or keyboard only. This is a very specific question so if no one knows then I’m still happy.
Thank you, Dist.