Add dialogs to Messaging section

[emplums]

I noticed that the Messaging section doesn't include anything about details-dialog elements that are frequently used to confirm actions or provide more information. Though we don't maintain details-dialog I still think it would make sense to provide usage guidelines for them as they are frequently used bits of our UI.

Example of a details-dialog being used to confirm actions:

It also seems anti-pattern to put a question in the header/title of the dialog - maybe we could provide some usage guidelines for that as well.