multi: announce Keysend feature bit

In this commit, we add the keysend feature bit to our NodeAnnouncement
if the accept-keysend option is set.

feature/deps.go

@@ -69,6 +69,9 @@ var deps = depDesc{
 		lnwire.ExplicitChannelTypeOptional:  {},
 		lnwire.AnchorsZeroFeeHtlcTxOptional: {},
 	},
+	lnwire.KeysendOptional: {
+		lnwire.TLVOnionPayloadOptional: {},
+	},
 }
 
 // ValidateDeps asserts that a feature vector sets all features and their