Add tabs

### Your use case

I would love tabs in **Element Desktop**.

This is not about Element Web, which would be fine if element-hq/element-web#26231 can be fixed.

#### What would you like to do?

Have multiple tabs with different rooms (and currently scrolled to position) open at the same time.

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

Multitasking. Example: To be able to switch to some other room without having to close current room (loose scroll position, forget about that I was in that room, etc..)

I have 4 applications always open on my screen:

- Browser (has tabs)
- Terminal (has tabs)
- Mail client (has tabs)
- Element

A browser without tabs would be unthinkable for me. I think the same would be true if Element had tabs.

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

As usual (like in web browsers).

### Have you considered any alternatives?

_No response_

### Additional context

_No response_