Implement home screen activity indicators

Riot/Modules/Application/AppNavigator.swift

@@ -15,6 +15,7 @@
 //
 
 import Foundation
+import CommonKit
 
 /// AppNavigatorProtocol abstract a navigator at app level.
 /// It enables to perform the navigation within the global app scope (open the side menu, open a room and so on)
@@ -26,4 +27,12 @@ protocol AppNavigatorProtocol {
     /// Navigate to a destination screen or a state
     /// Do not use protocol with associatedtype for the moment like presented here https://www.swiftbysundell.com/articles/navigation-in-swift/#where-to-navigator use a separate enum
     func navigate(to destination: AppNavigatorDestination)
+    
+    /// Add loading activity to an app-wide queue of other activitie
+    ///
+    /// If the queue is empty, the activity will be displayed immediately, otherwise it will be pending
+    /// until the previously added activities have completed / been cancelled.
+    ///
+    /// To remove an activity indicator, cancel or deallocate the returned `Activity`
+    func addLoadingActivity() -> Activity
 }