Initial integration of RTE (#1464)

* Initial integration of RTE

* Fix `clipped`, `focused` and composer view type

* Remove horizontal padding

* Add `ComposerToolbar` mock

* Restore `composerFocusedSubject`

* Allow using HTML from RTE on message sent

* Fix new message content API

* Add feature flag for Rich Text Editor

ElementX/Sources/Application/AppSettings.swift

@@ -40,6 +40,7 @@ final class AppSettings {
         case notificationSettingsEnabled
         case swiftUITimelineEnabled
         case pollsInTimeline
+        case richTextEditorEnabled
     }
     
     private static var suiteName: String = InfoPlistReader.main.appGroupIdentifier
@@ -237,4 +238,7 @@ final class AppSettings {
 
     @UserPreference(key: UserDefaultsKeys.pollsInTimeline, defaultValue: false, storageType: .userDefaults(store))
     var pollsInTimelineEnabled
+
+    @UserPreference(key: UserDefaultsKeys.richTextEditorEnabled, defaultValue: false, storageType: .userDefaults(store))
+    var richTextEditorEnabled
 }