Addons aren't able to send chat messages. The best they can do is pre-fill the chat message, but then you'll need to press enter to send it.
There is an add-on which can do that, but I don't think it'd be very useful with gamepad. There might be some other addons around which work better with gamepad. https://www.esoui.com/downloads/info1303-Notes.html

You need a chatpad