Ability to add a caption when forwarding a message

[ara4n]

Options for doing this include:

• Captioning it as if it were an image (if we had a generic 'human representation form of an event) method for doing this
• Extending the new rich quoting stuff - this is probably the best bet, actually.

[lampholder]

I'm not a fan of the current forward message UX, so I'd be reluctant to add additional stuff on top of it.

@ara4n What's the use case for this?

[MurzNN]

Good solution for this feature is implement message attachments, here is my feature request about this: https://github.com/matrix-org/matrix-doc/issues/2289