readme: add links and branches

README.md

@@ -2,7 +2,7 @@
 
 ## About
 
-InvenioRDM user documentation web site.
+This is the source of InvenioRDM user documentation web site. You can view the documentation for the current release of InvenioRDM at [https://inveniordm.docs.cern.ch/]( https://inveniordm.docs.cern.ch/), which tracks the `production` branch of this repository. You can see the documentation for the in-development next version of InvenioRDM at [https://inveniordm-dev.docs.cern.ch/](https://inveniordm-dev.docs.cern.ch/), which tracks the `master` branch of this repository.
 
 ## Running