XML's implementation for this is surprisingly intuitive. But to be fair, who tries to use JSON for modelling something like this? You're better off just embedding the XML in a JSON string:

{"markup": "<div>The <a href=\"https://www.json.org/\">JSON format</a> was invented by <em>Douglas Crockford</em>.</div>"}

Most JSON is consumed in the browser, which also has an XML/HTML parser engine sitting alongside the JSON one.