Move priority queue to pq package; improve docs.

binheap/lib.go

@@ -1,8 +1,9 @@
+// Package binheap implements a binary max-heap.
 package binheap
 
 import "golang.org/x/exp/constraints"
 
-// H is a generic, non-concurrent binary max-heap.
+// H is a binary max-heap.
 //
 // `I` is the type of the priority IDs, and `E` the type of the elements.
 type H[I constraints.Ordered, E any] struct {