feat: Add a placeholder for image attachments in conversations view (#8969)

We analyze an image to get it's height and width. On the frontend, we would show a placeholder with the corresponding width and height until the images are loaded properly.

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Co-authored-by: Shivam Mishra <scm.mymail@gmail.com>

app/views/api/v1/accounts/conversations/attachments.json.jbuilder

@@ -5,6 +5,8 @@ json.payload @attachments do |attachment|
   json.file_size attachment.push_event_data[:file_size]
   json.file_type attachment.push_event_data[:file_type]
   json.extension attachment.push_event_data[:extension]
+  json.width attachment.push_event_data[:width]
+  json.height attachment.push_event_data[:height]
   json.created_at attachment.message.created_at.to_i
   json.sender attachment.message.sender.push_event_data if attachment.message.sender
 end