feat: add log printing when peer added and removed table

[elecbug]

As of now, I don't think there is a major log in Kademlia that certainly can determine that a peer has been added.

The login 'msg': 'peer found' output, which is called prior to the commit, is only an possibility to add for the peer, and the fact that 'rt.PeerAdd()', which is actually called when a peer is added, is an empty function makes it difficult to measure the performance of Kademlia.

		PeerRemoved: func(p peer.ID) {
			log.Debugw("peer removed", "peer", p)
		},
		PeerAdded: func(p peer.ID) {
			log.Debugw("peer added", "peer", p)
		},

Thus, a simple log-add syntax was added.

[guillaumemichel]

Makes sense, thanks @elecbug!