Add hide-chats-list-in-forums setting.

Telegram/SourceFiles/settings/settings_experimental.cpp

@@ -18,6 +18,7 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 #include "core/application.h"
 #include "core/launcher.h"
 #include "chat_helpers/tabbed_panel.h"
+#include "dialogs/dialogs_widget.h"
 #include "lang/lang_keys.h"
 #include "mainwindow.h"
 #include "media/player/media_player_instance.h"
@@ -137,6 +138,7 @@ void SetupExperimental(
 	};
 
 	addToggle(ChatHelpers::kOptionTabbedPanelShowOnClick);
+	addToggle(Dialogs::kOptionForumHideChatsList);
 	addToggle(Core::kOptionFractionalScalingEnabled);
 	addToggle(Window::kOptionViewProfileInChatsListContextMenu);
 	addToggle(Ui::GL::kOptionAllowLinuxNvidiaOpenGL);