Mention set/bag ops in junctive section

Author: TimToady

S03-operators.pod

@@ -3229,6 +3229,10 @@ corresponding list operators.  However, junctive methods on a hash
 make a junction of only the hash's keys.  Use the listop form (or an
 explicit C<.pairs>) to make a junction of pairs.
 
+The various operators for sets and bags (intersection, union,
+etc.) also have junctive precedence (except for those that return Bool,
+which are instead classified as chaining operators).
+
 =head1 Comparison semantics
 
 =over