implement using custom sort function on an update struct

rerun benchmarks

day-05/internal/update/update.go

@@ -0,0 +1,20 @@
+package update
+
+import "slices"
+
+type Update struct {
+	Pages []int
+}
+
+func (u Update) Sort(orderings map[int][]int) {
+	slices.SortFunc(u.Pages, func(p, q int) int {
+		v, ok := orderings[p]
+		if ok {
+			if slices.Contains(v, q) {
+				return -1
+			}
+			return 1
+		}
+		return 1
+	})
+}