OPAM Installation.

README.md

@@ -73,6 +73,7 @@ Aura Engine is the play-out engine of the Aura Radio Software Suite. Aura stands
 
 * **Python**: https://docs.python.org/
 * **Redis**: https://redis.io/
+* **OPAM (OCaml Package Manager)**: https://opam.ocaml.org/
 * **Liquidsoap**: https://www.liquidsoap.info/doc-1.4.0/
 * **Jack Audio**: https://jackaudio.org/
 * **Flask**: https://palletsprojects.com/p/flask/