Scheduled messages

### Your use case

#### What would you like to do?
I would like to be able to schedule a message to be send at a preset later time

#### Why would you like to do it?
I often need to send myself as well as others a timed message at a later point in time

#### How would you like to achieve it?
When I long-press on the Send-button, I would like a pop-up option to schedule the entered message

### Have you considered any alternatives?

I have managed to use a workaround using the remind-feature of Maubot but it is a bit of a hassle and not easy to teach to less tech savy people I need to communicate with.

### Additional context

_No response_

### Are you willing to provide a PR?

No