@rbartlet
Thanks, but when call this method window.Twitch.ext.send I get response {"message":"Client-ID not provided"} , I have debugged the code reaching the file:line extension-frame.js:27 that send the request (using fetch function) without required headers documented in this curl command send-extension-pubsub-message, so I think that fetch method in that file should contains additional headers like Authorization and Client-Id. Any explanations for this?
I also tried to use the curl command it works fine and the video overlay received the message fine, but when run it via jQuery ajax I got CORS error.