Add OpenWISP to Network configuration management tools (#449)

As mentioned in #439

Co-authored-by: nodiscc <nodiscc@gmail.com>

README.md

@@ -575,12 +575,14 @@ _See also: [IT Asset Management]([Ralph](#it-asset-management))_
 *Network configuration management tools.*
 
 - [GNS3](https://www.gns3.com/) - Graphical network simulator that provides a variety of virtual appliances. ([Source Code](https://github.com/GNS3/gns3-gui/)) `GPL-3.0` `Python`
+- [OpenWISP](https://openwisp.org/) - Open Source Network Management System for OpenWRT based routers and access points. ([Demo](https://openwisp.org/demo.html), [Source Code](https://github.com/openwisp)) `GPL-3.0` `Python` 
 - [Oxidized](https://github.com/ytti/oxidized) - Network device configuration backup tool. `Apache-2.0` `Ruby`
 - [phpIPAM](http://phpipam.net/) - Open source IP address management with PowerDNS integration. ([Source Code](https://github.com/phpipam/phpipam)) `GPL-3.0` `PHP`
 - [RANCID](http://www.shrubbery.net/rancid/) - Monitor network devices configuration and maintain history of changes. ([Source Code](https://github.com/haussli/rancid)) `BSD-3-Clause` `Perl/Shell`
 - [rConfig](http://www.rconfig.com/) - Network device configuration management tool. ([Source Code](https://github.com/rconfig/rconfig)) `GPL-3.0` `PHP`
 
 
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