fix: update greeting postback_id docs

Author: mdojwa

src/pages/management/configuration-api/v3.6/index.mdx

@@ -1977,10 +1977,10 @@ Creates a new greeting with specified parameters within a license.
 | `elements[].image.alternative_text` | no     | `string`  | Alternative text for the image                                                                                                                                                                                                                   |
 | `elements[].buttons`              | no       | `array`   | Displays buttons. Can contain up to 13 `button` objects.                                                                                                                                                                                         |
 | `elements[].buttons[].text`       | yes      | `string`  | Text displayed on a button.                                                                                                                                                                                                                      |
-| `elements[].buttons[].type`       | yes      | `string`  | Defines the behavior after a user clicks the button. Should be used together with `elements.buttons.value`. Possible values: `webview`, `message`, `url`, `phone`. [More...](/extending-chat-widget/rich-messages/#getting-started) |
+| `elements[].buttons[].type`       | yes      | `string`  | Defines the behavior after a user clicks the button. Should be used together with `elements.buttons.value`. Possible values: `webview`, `message`, `url`, `phone`. [More...](/extending-chat-widget/rich-messages/#getting-started)              |
 | `elements[].buttons[].value`      | yes      | `string`  | Should be used together with `elements.buttons.type`. You can use this field to give the rich message of a `webview` type (a Moment) a custom title. [More...](/extending-chat-widget/chat-widget-moments/#how-to-start)                         |
-| `elements[].buttons[].postback_id` | yes     | `string`  | A description of the sent action. Describes the action sent via `send_rich_message_postback`. [More...](/extending-chat-widget/rich-messages/#getting-started)                                                                      |
-| `elements[].buttons[].role`<sup>**1**</sup>   | no      | `string`   | Button role.                                                                                                                                                                                   |
+| `elements[].buttons[].postback_id` | yes     | `string`  | A unique (in the whole greeting) ID of the button. It will be used to report the button actions using [`send_greeting_postback`](/messaging/customer-chat-api/v3.6/#send-greeting-postback)                                                      |
+| `elements[].buttons[].role`<sup>**1**</sup>   | no      | `string`   | Button role.                                                                                                                                                                                                                         |
 
 
 **1)** Possible values for the `elements[].buttons[].role` parameter: