AppFlowy/app_flowy/packages/flowy_editor/example/assets/block_document.fdoc

[
   {
      "insert":"This is a checkbox"
   },
   {
      "attributes":{
         "list":"checked"
      },
      "insert":"\n"
   },
   {
      "insert": {
         "flutter_logo": ""
      },
      "attributes":{
         "size": 50.0
      }
   },
   {
    "insert":"\n"
   }
]