chore: add project status section to the readme

also add not that Elastic does not support this library, just in case

readme.md

@@ -1,8 +1,13 @@
 [![Build Status](https://travis-ci.org/elastic/esqueue.svg?branch=master)](https://travis-ci.org/elastic/esqueue)
+[![Project Status](https://img.shields.io/badge/status-experimental-orange.svg)](https://github.com/elastic/esqueue#project-status)
 
 # esqueue
 
-`esqueue` is an Elasticsearch-powered job queue
+`esqueue` is an Elasticsearch-powered job queue. This is not supported by Elastic.
+
+## Project Status
+
+While it's believed to be pretty stable, this library isn't really being used anywhere. Issues and PRs are welcome, but it isn't actively being developed. As such, it doesn't get a lot of stress testing, and I don't recommend you rely too heavily on it, hence its experimental status.
 
 ## Installation