TextEditor: add json indenter

Use an EditorFactory that sets up a custom indenter for json files.

Change-Id: Id5ade9f9f551835131a62e381a972f0b6032e7c0
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/texteditor/jsoneditor.h

@@ -0,0 +1,16 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
+
+#pragma once
+
+#include "texteditor.h"
+
+namespace TextEditor::Internal {
+
+class JsonEditorFactory final : public TextEditorFactory
+{
+public:
+    JsonEditorFactory();
+};
+
+} // TextEditor::Internal