Add 90 minute network deck to README.md

[taruch]

Area

Ansible Network Automation Workshop

Proposed Changes

https://docs.google.com/presentation/d/10QhALqWVwsZ1GYfzxAejsKmBB2QeoWo_SNkB1RnzcQo/edit?usp=sharing

This was the Network Workshop deck presented at that last NAPS workshop wednesday.