[Story] Render typing notification

[bmarty]

Description

• As a member of a room viewing the timeline, I want to see when one or several other users are typing a message so that I can expect a new message from them.

• No typing notification is displayed when the user is on the room list.

Rust implementation: https://github.com/matrix-org/matrix-rust-sdk/pull/3059. Not that Rust does not filter out the current user (and I think this is fine), the filtering has to be done on the app side.

Figma: https://www.figma.com/file/Ni6Ii8YKtmXCKYNE90cC67/Timeline-(new)?type=design&node-id=254%3A49852&mode=design&t=LUBT4dAoV6qjfqV9-1 Still need to take a decision about how the scrolling will behave.

Strings have been added to Localay with the prefix screen_room_typing_:

  <plurals name="screen_room_typing_many_members">
    <item quantity="one">"%1$s, %2$s and %3$d other"</item>
    <item quantity="other">"%1$s, %2$s and %3$d others"</item>
  </plurals>
  <plurals name="screen_room_typing_notification">
    <item quantity="one">"%1$s is typing"</item>
    <item quantity="other">"%1$s are typing"</item>
  </plurals>
  <string name="screen_room_typing_two_members">"%1$s and %2$s"</string>

This should be enough to cover all the cases, and do a proper formatting, but let me know if there are any questions.

Acceptance criteria

• When one or several people are typing a message in a room, I can see it in the timeline.

Size estimate

None

Dependencies

• We need some design to decide how we can render the typing notification in the timeline.

Out of scope

• Nothing

Open questions

### Questions

Subtasks

### Android
- [ ] https://github.com/element-hq/element-x-android/issues/2242

### iOS
- [ ] https://github.com/element-hq/element-x-ios/issues/2349

### Rust
- [ ] https://github.com/matrix-org/matrix-rust-sdk/pull/3059

### Other

[bmarty]

We have some design here: https://www.figma.com/file/Ni6Ii8YKtmXCKYNE90cC67/Timeline-(new)?type=design&node-id=254%3A49852&mode=design&t=LUBT4dAoV6qjfqV9-1

We still need to decide how the typing notification will scroll.

[bmarty]

The typing notification will scroll like a message (so it's like a regular timeline item).