Add next gen HTML parser feature flag

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

@@ -52,6 +52,8 @@ protocol DeveloperOptionsProtocol: AnyObject {
     var fuzzyRoomListSearchEnabled: Bool { get set }
     var lowPriorityFilterEnabled: Bool { get set }
     var knockingEnabled: Bool { get set }
+    
+    var nextGenHTMLParserEnabled: Bool { get set }
 }
 
 extension AppSettings: DeveloperOptionsProtocol { }