message: docs: Update Usage docs to include Domains in Promise support
diff: @@ -90,6 +90,8 @@ A context might also correspond to, say, a connection lifecycle or a job being h
  Notable keys that you might set include ``user``, ``tags``, and ``extra``.
  These types of extra context data are detailed more under :ref:`raven-node-additional-data`.
  +Since ``domains`` are not supported in native Promise until Node v8.0.0, the Node LTS version ``>=8.0.0`` environment is required if you want to manage different contexts in Promises. Context for regular ``context/wrap`` and instrumentation is working prior to 8.x just fine. It'll just be skipped and will use globally set context data.
  +
  Tracking Users
  --------------
  