[AIRFLOW-XXX] Add Fathom Health to readme

Author: r39132

README.md

@@ -153,6 +153,7 @@ Currently **officially** using Airflow:
 1. [Enigma](https://www.enigma.com) [[@hydrosquall](https://github.com/hydrosquall)]
 1. [eRevalue](https://www.datamaran.com) [[@hamedhsn](https://github.com/hamedhsn)]
 1. [evo.company](https://evo.company/) [[@orhideous](https://github.com/orhideous)]
+1. [Fathom Health](https://www.fathomhealth.co/)
 1. [Flipp](https://www.flipp.com) [[@sethwilsonwishabi](https://github.com/sethwilsonwishabi)]
 1. [Format](https://www.format.com) [[@format](https://github.com/4ormat) & [@jasonicarter](https://github.com/jasonicarter)]
 1. [FreshBooks](https://github.com/freshbooks) [[@DinoCow](https://github.com/DinoCow)]