Video playback (#308)

* Create media player screen

* Introduce `FileCache` to cache message attachments

* Add file loading functionality into the media provider

* Process tap action on timeline items

* Pass item taps to view model

* Navigate to media player on view model callback

* Commit project file

* Add changelog

* Rename media to video

* Add a loader when large videos being processed

* Add back button explicitly on video screen, fixes for light scheme

* Handle right swipe to dismiss video

ElementX/Sources/Screens/RoomScreen/RoomScreenViewModelProtocol.swift

@@ -18,6 +18,7 @@ import Foundation
 
 @MainActor
 protocol RoomScreenViewModelProtocol {
+    var callback: ((RoomScreenViewModelAction) -> Void)? { get set }
     var context: RoomScreenViewModelType.Context { get }
 
     func stop()