MarkdownView: Merge into TextEditor

Make it a bit more compact, too.

Change-Id: I448164371c5a1d6969a292feba17caa2826f58c3
Reviewed-by: Tasuku Suzuki <tasuku.suzuki@signal-slot.co.jp>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/texteditor/markdowneditor.h

@@ -0,0 +1,16 @@
+// Copyright (C) 2023 Tasuku Suzuki
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
+
+#pragma once
+
+#include <coreplugin/editormanager/ieditorfactory.h>
+
+namespace TextEditor::Internal {
+
+class MarkdownEditorFactory final : public Core::IEditorFactory
+{
+public:
+    MarkdownEditorFactory();
+};
+
+} // TextEditor::Internal