[Story] Suggestion for room alias

[bmarty]

Description

• As a user
• I want to easily insert link to other room in a message
• by typing # and some character and have a list of room suggestions

Could be something like:

Acceptance criteria

• TBD

Leads

• Tech:
• Design:

Size estimate

M

Dependencies

• None

Out of scope

• Nothing

Open questions

### Questions

Subtasks

### Android
- [ ] https://github.com/element-hq/element-x-android/issues/2907

### iOS

### Rust

### Other

Sign-off

Android

• Design sign-off on completion
• QA sign-off on completion
• Product sign-off on completion

iOS

• Design sign-off on completion
• QA sign-off on completion
• Product sign-off on completion

[bmarty]

Note: this has been implemented on Android under a disabled feature flag in element-hq/element-x-android#3322