Implement mix update script

lib/mix/tasks/heroicons/update.ex

@@ -0,0 +1,22 @@
+defmodule Mix.Tasks.Heroicons.Update do
+  @moduledoc """
+  Update heroicons.
+  By default, it downloads the latest version but you
+  can configure it in your config files, such as:
+      config :heroicons, :version, "#{Heroicons.latest_version()}"
+  """
+
+  @shortdoc "Update heroicons assets"
+
+  use Mix.Task
+
+  @impl true
+  def run(args) do
+    {_opts, args} = OptionParser.parse!(args, strict: [])
+
+    case args do
+      [] -> Heroicons.update()
+      _ -> Mix.raise("Invalid arguments, expected: mix heroicons.update")
+    end
+  end
+end