Add info about the integration with Apache Nifi

I wrote an article on LinkedIn detailing how to use fake-gcs-server with Apache Nifi: https://www.linkedin.com/pulse/how-configure-apache-nifi-use-fake-gcs-local-vincenzo-lombardo-r1vuf/?trackingId=jwNDr49QQFKHjGMD6nmcxA%3D%3D
