function isElementAllowed(element) {
  const allowed = TEXT_LEVEL_ELEMENTS[element.namespaceURI];
  return allowed && allowed.includes(element.localName);
}
Check if element is allowed in the translation.

This method is used by the sanitizer when the translation markup contains
an element which is not present in the source code.

@param   {Element} element
@returns {boolean}
@private