chore(README): update README

add a link to the wiki

Author: huertas

README.md

@@ -16,6 +16,8 @@ As a middleware toolkit, PowerAPI offers the capability of assembling power mete
 
 PowerAPI is an open-source project developed by the [Spirals research group](https://team.inria.fr/spirals) (University of Lille 1 and Inria) and fully managed with [sbt](http://www.scala-sbt.org).
 
+The documentation is available [here](https://github.com/Spirals-Team/powerapi/wiki/Getting-started).
+
 ## Mailing list
 You can follow the latest news and asks questions by subscribing to our <a href="mailto:sympa@inria.fr?subject=subscribe powerapi">mailing list</a>.