Augmented-by Addition to the YANG Library

"YANG Library" specifies the YANG module "ietf-yang-library" that provides information about the YANG modules, datastores, and datastore schemas used by a network management server. This document augments the "ietf-yang-library" to provide the augmented-by list. It facilitates the process of obtaining all dependencies between YANG modules, by querying the network management server's YANG library. This document updates RFC 8525, as the lists in Section 2 is modified to also include augmented-by list.