How can we add that htmlrules property in custom js"htmlRules":
{"genericHtml": {"converters": [{"type": "video","name":
"video","detectors": [{"type": "element","tagName":
"video"}],"thumbnailMaxWidth": 240,"keepEmptyContainers": true},
{"type": "imagethumb","name": "imagethumb","detectors": [{"type":
"element","tagName": "img"}],"thumbnailMaxWidth":
240,"keepEmptyContainers": true}