Sending an Agent Chat Message from a BUI Extension

Summary

I'm looking for a supported way to send an agent message in a chat from a BUI Extension.

Content

I am looking for a supported/official way to add an agent message to a chat from a BUI extension (like what PostMessage() does in the .NET API). I haven't been able to find anything in the Agent Browser UI Extensibility Framework or the REST APIs.

Thanks!

For more background info, here is a post I previously made. Since I was asking multiple questions in that post, and didn't specify that I'm looking for something official, I decided to ask again more specifically.