XHTML Extension Type ​

{
  "linkId": "2.1",
  "type": "display",
  "_text": {
    "extension": [
      {
        "url": "http://hl7.org/fhir/StructureDefinition/rendering-xhtml",
        "valueString": "<div><p>Basic XHTML content example for FHIR documentation.</p><img src='#image1' alt='sample' /></div>",
        "_valueString": {
          "extension": [
            {
              "url": "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-referencesContained",
              "valueReference": {
                "reference": "#image1"
              }
            }
          ]
        }
      }
    ]
  }
}