Add slack channel to README.md

Add slack channel to README

README.md

@@ -4,6 +4,11 @@
 
 The API gateway for [Aerie](https://github.com/NASA-AMMOS/aerie).
 
+## Need Help?
+
+- Join us on the [JPL Slack Grid](https://join.slack.com/share/enQtNjM2MjkwODY0MTk5MS1lNWU5MTA1MzQyNjQ0ZTJjOGFlOTljYTA2YjIxNWMxZGIyZjBjNTlkOTEwNjZmMGYwY2Y0ZTM1OGM4ZGQ5NmQ1) (#nasa-ammos-aerie-users)
+- Contact [email protected]
+
 ## Develop
 
 First make sure you have [Node.js LTS](https://nodejs.org) installed. Set the default `POSTGRES_USER` and `POSTGRES_PASSWORD` [environment variables](./docs/ENVIRONMENT.md), then do: