Direct Messages (DMs) with many people

### Your use case

#### What would you like to do?

Create a DM with more than 2 people in it.

#### Why would you like to do it?

I *think* I saw that this omission is a choice. I'm not sure if that is the case, but if so I think it is incorrect.

- Element Web allows you to create DM style rooms very easily, so More Than Two Direct Messages are already a thing in the Element ecosystem.
- I may be weird, but I expect that sort of functionality.
- I keep getting invites to rooms that are clearly attempts to create MTTDMs (mom creating a room named 'Sons').

The last bullet is an especially bad UX because I now have many pseudo-MTTDMs that are all named from the creators context (Sons, Boys, kids, 3kids). They keep getting created because element doesn't know to dedup them on creation. It also doesn't know that if I leave them that the room is functionally broken.

#### How would you like to achieve it?

We could

- Make MTTDMs a thing
- Add an option to ignore a room title and just display participants. Some sort of explicit "this is a DM" button.
- Argue with my mom

### Have you considered any alternatives?

_No response_

### Additional context

_No response_

### Are you willing to provide a PR?

No