Advanced delivery status

**Suggestion**
What would you like to see in Matrix? If your idea is vaguely complete enough, we
recommend submitting [an MSC](https://matrix.org/docs/spec/proposals) instead.

Currently, Matrix only allows to know when our message arrived to our homeserver. However, it would be desirable to know the following:

- Whether message arrived to the recipient's homeserver
- Whether message arrived to the recipient's device
- (The already possible, our homeserver)

This could maybe be implemented with state events, by making the recipient homeserver and device send those state events to a room (and all of its participants).
An MSC is outside of my capabilities i'm afraid.

Inspired by: https://github.com/vector-im/element-meta/issues/328

Read the Matrix spec proposal process at the linked MSC documentation and compare the delivery-status need with the linked Element issue. Done means a concrete, reviewed MSC defining the requested delivery states and their scope.

Written by the indexing model from the issue text.