message: document URI options
diff: @@ -71,7 +71,10 @@ class.
  You must specify the host to connect to using a
  [`mongocxx::uri`]({{< api3ref classmongocxx_1_1uri >}}) instance containing a
  [MongoDB URI](https://docs.mongodb.com/master/reference/connection-string/),
  -and pass that into the `mongocxx::client` constructor.
  +and pass that into the `mongocxx::client` constructor. For details regarding
  +supported URI options see the documentation for the version of libmongoc used
  +to build the C++ driver or for the [latest libmongoc release](
  +http://mongoc.org/libmongoc/current/mongoc_uri_t.html)
  The default `mongocxx::uri` constructor will connect to a
  server running on localhost on port `27017`:
  