function hasDirective(node, name, argument) {
  return Boolean(getDirective(node, name, argument))
}
Check whether the given start tag has specific directive.
@param {VElement} node The start tag node to check.
@param {string} name The directive name to check.
@param {string} [argument] The directive argument to check.
@returns {boolean} `true` if the start tag has the directive.