Add the spaces feature announcement sheet. (#4571)

ElementX/Sources/Application/Settings/AppSettings.swift

@@ -29,6 +29,7 @@ final class AppSettings {
     private enum UserDefaultsKeys: String {
         case lastVersionLaunched
         case seenInvites
+        case hasSeenSpacesAnnouncement
         case hasSeenNewSoundBanner
         case appLockNumberOfPINAttempts
         case appLockNumberOfBiometricAttempts
@@ -162,6 +163,9 @@ final class AppSettings {
     @UserPreference(key: UserDefaultsKeys.seenInvites, defaultValue: [], storageType: .userDefaults(store))
     var seenInvites: Set<String>
     
+    @UserPreference(key: UserDefaultsKeys.hasSeenSpacesAnnouncement, defaultValue: false, storageType: .userDefaults(store))
+    var hasSeenSpacesAnnouncement
+    
     /// Defaults to `true` for new users, and we use a migration to set it to `false` for existing users.
     @UserPreference(key: UserDefaultsKeys.hasSeenNewSoundBanner, defaultValue: true, storageType: .userDefaults(store))
     var hasSeenNewSoundBanner