Message list items should support timestamps as dates

[marcushellberg]

Describe your motivation

Right now, the API for message list item assumes you pass in a string for the time. If you pass in "right now", as in the API docs, it remains "right now" even if an hour passes.

Describe the solution you'd like

I would like the item to take a date object as the time. The message list should have a default formatter for times that can be overridden.

Describe alternatives you've considered

• Updating the entire message history every few seconds
• Not using relative times

Additional context

No response

[yuriy-fix]

Related issue: https://github.com/vaadin/web-components/issues/2060