modify README add image wireshark capture

Author: TeddyWiz

README.md

@@ -101,5 +101,7 @@ best fits for low-end Non-OS devices connecting to Ethernet for the Internet of
   </p>
 
    ## Test packet capture file
+   <p align="center">
+     <img width="60%" src="https://user-images.githubusercontent.com/48539052/55852389-ba949600-5b97-11e9-8824-91287170a243.png" />
+   </p>
     - [HTTP_Server_Packet.zip](https://github.com/WIZnet-ioLibrary/W6100EVB-HTTP_Server/files/3057274/HTTP_Server_Packet.zip)
-