lnwire+feature: add feature bit for script enforced lease support

feature/default_sets.go

@@ -64,4 +64,8 @@ var defaultSetDesc = setDesc{
 		SetInit:    {}, // I
 		SetNodeAnn: {}, // N
 	},
+	lnwire.ScriptEnforcedLeaseOptional: {
+		SetInit:    {}, // I
+		SetNodeAnn: {}, // N
+	},
 }