Update README.md

Author: ivarprudnikov

README.md

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 ## About
 
+![Preview of sample app](https://github.com/ivarprudnikov/use-python-in-node/raw/master/node-python-websockets-preview.png "Preview of sample app")
+
 This is a simple example of a _Node.js_ server with following features:
 - Enabled WebSocket communication
 - HTTP endpoint which runs `python` script synchronously and returns its output