[Promotion] Add new promotion rule that order contains selected item

With this checker you can set promotion i.e.:
```feature
    Background:
        Given I am logged in as user "klaus@example.com"
        And the following countries exist:
          | name    |
          | Poland  |
        And the following products exist:
          | name    | price |
          | Woody   | 15    |
        And the following promotions exist:
          | name          | description                |
          | Woody T-Shirt | Discount for Woody T-Shirt |
        And promotion "Woody T-Shirt" has following rules defined:
          | type         | configuration                     |
          | Contain item | variant: Woody T-Shirt,only: true |
        And promotion "Woody T-Shirt" has following actions defined:
          | type           | configuration |
          | Fixed discount | amount: 5     |

    Scenario: Contain item promotion is applied when the cart
              has required item
        Given I am on the store homepage
         When I add product "Woody T-Shirt" to cart, with quantity "1"
         Then I should be on the cart summary page
          And "Promotion total: -€5.00" should appear on the page
          And "Grand total: €10.00" should appear on the page
```

I was not sure about, but we could adjust code and allow to check multiple items not only one as now, what do you think?