A TeeDestination allows writing to two destinations at once. For example the output of a transformation
can be written simultaneously to a Serializer and to a second Transformation. By chaining together a number
of TeeDestinations it is possible to write to any number of destinations at once.
config - The Saxon configuration. This is supplied so that the destination can
use information from the configuration (for example, a reference to the name pool)
to construct or configure the returned Receiver.
the Receiver to which events are to be sent. It is the caller's responsibility to
initialize this Receiver with a PipelineConfiguration before calling
its open() method.