* Initial support for member suggestion (search and UI)
* Add custom `BottomSheetScaffold` implementation to workaround several scrolling bugs
* Start searching as soon as `@` is typed, add UI following initial designs
* Extract suggestion processing code
* Extract component, add previews, fix tests
* Add tests
* Add exception from kover to the forked bottom sheet code
* Add a feature flag for mentions
- Extract composer & mention suggestions to their composable.
- Extract mentions suggestions processing to its own class.
- Add `MatrixRoom.canTriggerRoomNotification` function.
- Update strings and conditions for displaying the `@room` mention.
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Co-authored-by: ElementBot <benoitm+elementbot@element.io>
