Custom HTML for knowing when a user you to is writing you a message -- 2

I need to display a div box/ container when a user is writing a message to the current logged in user. I use [login to view URL] for logged in users on my site and have a wokring sign up, login, logout firebase html pages. I am looking for a custom snipped ot code that I can run in webflow using the custom embed html feature. The box must show when the user on another machine starts typing, if there are no characters typed the box must hide. This must be done in realtime. You might need to use firebase or firestore to make it work.