Add wrapper for garnish/2 for phx event

lib/outlook/internal_tree.ex

@@ -27,6 +27,16 @@ defmodule Outlook.InternalTree do
     |> RawInternalBasic.partition_to_tunits()
   end
 
+  def add_phx_click_event(tree, opts) do
+    phx_opts = %{
+      "phx-click": Keyword.get(opts, :click),
+      "phx-target": Keyword.get(opts, :target) |> to_string,
+      "phx-value-nid": fn n -> n.nid end
+    }
+    options = Map.put(%{}, Keyword.get(opts, :nodes, :elements), phx_opts)
+    garnish(tree, options)
+  end
+
   def garnish(tree, options) do
     options = Enum.reduce(
       ~w(el_ids el_names tu_ids)a,