Add a Link New Device screen (behind a feature flag). (#4811)

ElementX/Sources/Screens/Settings/DeveloperOptionsScreen/DeveloperOptionsScreenModels.swift

@@ -57,6 +57,7 @@ protocol DeveloperOptionsProtocol: AnyObject {
     var linkPreviewsEnabled: Bool { get set }
     
     var spaceSettingsEnabled: Bool { get set }
+    var linkNewDeviceEnabled: Bool { get set }
 }
 
 extension AppSettings: DeveloperOptionsProtocol { }

ElementX/Sources/Screens/Settings/DeveloperOptionsScreen/View/DeveloperOptionsScreen.swift

@@ -34,6 +34,9 @@ struct DeveloperOptionsScreen: View {
             }
             
             Section("General") {
+                Toggle(isOn: $context.linkNewDeviceEnabled) {
+                    Text("Link new device with QR code")
+                }
                 Toggle(isOn: $context.spaceSettingsEnabled) {
                     Text("Space settings")
                 }