DOCS: Added IMAP URL example for listing new messages

In addition to listing the folder contents, in the URL examples, added
an example to list the new messages waiting in the user's inbox.

docs/libcurl/curl_easy_setopt.3

@@ -825,6 +825,9 @@ imap://user:password@mail.example.com - Performs a top level folder list
 imap://user:password@mail.example.com/INBOX - Performs a folder list on the
 user's inbox
 
+imap://user:password@mail.example.com/INBOX -X "SEARCH NEW" - This lists the
+new messages in the user's inbox.
+
 imap://user:password@mail.example.com/INBOX/;UID=1 - Selects the user's inbox
 and fetches message 1