Update list of utilities

Author: wooorm

readme.md

@@ -449,8 +449,7 @@ unist:
 *   [`unist-util-find-before`](https://github.com/syntax-tree/unist-util-find-before)
     — Find a node before another node
 *   [`unist-util-flat-filter`](https://github.com/unicorn-utterances/unist-util-flat-filter)
-    — Create a new tree with all nodes that pass the given function without
-    references to the parent
+    — Flat map version of `unist-util-filter`
 *   [`unist-util-flatmap`](https://gitlab.com/staltz/unist-util-flatmap)
     — Create a new tree by expanding a node into many
 *   [`unist-util-generated`](https://github.com/syntax-tree/unist-util-generated)
@@ -469,6 +468,8 @@ unist:
     — `parent` references on nodes
 *   [`unist-util-position`](https://github.com/syntax-tree/unist-util-position)
     — Get positional info of nodes
+*   [`unist-util-reduce`](https://github.com/GenerousLabs/unist-util-reduce)
+    — Recursively reduce a tree
 *   [`unist-util-remove`](https://github.com/syntax-tree/unist-util-remove)
     — Remove nodes from trees
 *   [`unist-util-remove-position`](https://github.com/syntax-tree/unist-util-remove-position)