Add Matrix chat support

[daltinn]

Please, add support for matrix chat - https://matrix.org/

[yncyrydybyl]

That's an really old one.

It's possible to create a webhook via matrix-hookshot. This can create webhooks and inject transformation code in javascript to format the message.

https://matrix-org.github.io/matrix-hookshot/latest/setup/webhooks.html#payload-formats

I started a transformation gist to get an idea.

Where can I see how the payload is structured?