docs: add metadata prop

Author: dgarcia360

docs/customization/layout.mdx

@@ -48,6 +48,7 @@ The table below lists all the available properties that modify the chatbot modal
 | **Layout**             |  |  |
 | `disable-input`        | **Type**: `boolean`<br />**Default value**: `false`<br /><br />When set to `true`, the user input field is disabled. |
 | `email`                | **Type**: `string`<br />**Default value**: ``<br /> An email address or ID for conversation tracking. This ID will be associated with the chat session in your project dashboard for analytics and user tracking purposes. |
+| `metadata`             | **Type**: `string`<br />**Default value**: ``<br /><br />Custom metadata to attach to chat sessions. Use this to pass additional contextual information (e.g., user plan, page URL, or other identifiers) that will be associated with the conversation for analytics purposes. |
 | `expand-modal`         | **Type**: `boolean`<br />**Default value**: `false`<br /><br />When set to `true`, the chat modal opens in its expanded state by default. |
 | `hide-close-button`    | **Type**: `boolean`<br />**Default value**: `false`<br /><br />When set to `true`, the close icon hides. |
 | `hide-expand-button`   | **Type**: `boolean`<br />**Default value**: `false`<br /><br />When set to `true`, the expand button icon hides. |