Instrument missing screen metrics (#5764)

* Instrument missing screen metrics

- Done

Riot/Modules/Analytics/AnalyticsScreenTracker.swift

@@ -0,0 +1,49 @@
+// 
+// Copyright 2021 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import Foundation
+
+/// An object to report the screen's display to the `Analytics` object.
+@objcMembers class AnalyticsScreenTracker: NSObject {
+    
+    // MARK: - Properties
+    
+    /// The screen being tracked.
+    private let screen: AnalyticsScreen
+
+    // MARK: - Setup
+    
+    /// Create a new screen tracker for the specified screen.
+    /// - Parameter screen: The screen that should be reported.
+    init(screen: AnalyticsScreen) {
+        self.screen = screen
+        super.init()
+    }
+    
+    // MARK: - Public
+    
+    /// Send screen event without duration
+    func trackScreen() {
+        Analytics.shared.trackScreen(screen)
+    }
+    
+    // MARK: static method
+    
+    static func trackScreen(_ screen: AnalyticsScreen) {
+        Analytics.shared.trackScreen(screen)
+    }
+    
+}