readme DOC add docs link badge

Author: michalvasko

README.md

@@ -2,6 +2,7 @@
 
 [![BSD license](https://img.shields.io/badge/License-BSD-blue.svg)](https://opensource.org/licenses/BSD-3-Clause)
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 **libnetconf2** is a NETCONF library in C intended for building NETCONF clients