add interface and annotation object definition for ThemeKey operator and property

<?php

/**

 * @file

 * Provides Drupal\themekey\OperatorInterface

 */

namespace Drupal\themekey;

use Drupal\Component\Plugin\PluginInspectionInterface;

/**

 * Defines an interface for ThemeKey operator plugins.

 */

interface OperatorInterface extends PluginInspectionInterface {

  /**

   * Return the name of the ThemeKey operator.

   *

   * @return string

   */

  public function getName();

  /**

   * Return the Description of the ThemeKey operator.

   *

   * @return float

   */

  public function getDescription();

}

<?php

/**

 * @file

 * Provides Drupal\themekey\PropertyInterface

 */

namespace Drupal\themekey;

use Drupal\Component\Plugin\PluginInspectionInterface;

/**

 * Defines an interface for ThemeKey property plugins.

 */

interface PropertyInterface extends PluginInspectionInterface {

  /**

   * Return the name of the ThemeKey property.

   *

   * @return string

   */

  public function getName();

  /**

   * Return the Description of the ThemeKey property.

   *

   * @return float

   */

  public function getDescription();

}