doc: buy me a coffee

Author: fcwu

README.md

@@ -3,6 +3,7 @@ docker-ubuntu-vnc-desktop
 
 [![Docker Pulls](https://img.shields.io/docker/pulls/dorowu/ubuntu-desktop-lxde-vnc.svg)](https://hub.docker.com/r/dorowu/ubuntu-desktop-lxde-vnc/)
 [![Docker Stars](https://img.shields.io/docker/stars/dorowu/ubuntu-desktop-lxde-vnc.svg)](https://hub.docker.com/r/dorowu/ubuntu-desktop-lxde-vnc/)
+[![Buy Me a Coffee at ko-fi.com](https://az743702.vo.msecnd.net/cdn/kofi2.png?v=0)](https://ko-fi.com/A4602SFN')
 
 Docker image to provide HTML5 VNC interface to access Ubuntu 16.04 LXDE desktop environment.