Update download.ex w/ placeholders

lib/playwright/page/download.ex

@@ -1,3 +1,31 @@
-defmodule Playwright.Page.Download do
+defmodule Playwright.Download do
   @moduledoc false
+
+  # @spec cancel(t()) :: :ok
+  # def cancel(download)
+
+  # @spec create_read_stream(t()) :: readable()
+  # def create_read_stream(download)
+
+  # @spec delete(t()) :: :ok
+  # def delete(download)
+
+  # @spec failure(t()) :: nil | binary()
+  # def failure(download)
+
+  # @spec page(t()) :: Page.t()
+  # def page(download)
+
+  # @spec path(t()) :: binary()
+  # def path(download)
+
+  # @spec save_as(t(), binary()) :: :ok
+  # def save_as(download, path)
+
+  # @spec suggested_filename(t()) :: binary()
+  # def suggested_filename(download)
+
+  # @spec url(t()) :: binary()
+  # def url(download)
+
 end