Use unordered_set instead of set

Author: spicychickensauce

c_src/lazy_html.cpp

@@ -717,7 +717,7 @@ FINE_NIF(child_nodes, 0);
 
 ExLazyHTML parent_node(ErlNifEnv *env, ExLazyHTML ex_lazy_html) {
   auto nodes = std::vector<lxb_dom_node_t *>();
-  auto inserted_nodes = std::set<lxb_dom_node_t *>();
+  auto inserted_nodes = std::unordered_set<lxb_dom_node_t *>();
 
   for (auto node : ex_lazy_html.resource->nodes) {
     auto parent = node->parent;