feat(LinkedIn Node): Add support for Article thumbnails (#7489)

Github issue / Community forum post (link here to close automatically):
https://community.n8n.io/t/linkedin-post-not-showing-image-for-url/10789/


![image](https://github.com/n8n-io/n8n/assets/4688521/5142b984-f531-4731-8510-c7136087861e)

This adds a new property to add a thumbnail binary property for articles
this fixes the previews no longer working because of the LinkedIn API
change.

![image](https://github.com/n8n-io/n8n/assets/4688521/76271525-5791-4bdc-ae73-1fdbb3986694)

packages/nodes-base/nodes/LinkedIn/PostDescription.ts

@@ -172,6 +172,18 @@ export const postFields: INodeProperties[] = [
 					},
 				},
 			},
+			{
+				displayName: 'Thumbnail Binary Property',
+				name: 'thumbnailBinaryPropertyName',
+				type: 'string',
+				default: 'data',
+				description: 'Object property name which holds binary data for the article thumbnail',
+				displayOptions: {
+					show: {
+						'/shareMediaCategory': ['ARTICLE'],
+					},
+				},
+			},
 			{
 				displayName: 'Title',
 				name: 'title',