docs: add NodeDownloader todo

lib/nodelix/node_downloader.ex

@@ -0,0 +1,21 @@
+defmodule Nodelix.NodeDownloader do
+  @moduledoc """
+  TODO
+  - fetch Node.js archive for a version and platform (https://nodejs.org/dist/v20.10.0/)
+  - fetch checksum file (https://nodejs.org/dist/v20.10.0/SHASUMS256.txt)
+  - fetch checksum file signature (https://nodejs.org/dist/v20.10.0/SHASUMS256.txt.sig)
+  - fetch Node.js signing keys list (https://raw.githubusercontent.com/nodejs/release-keys/main/keys.list)
+  - fetch keys (https://raw.githubusercontent.com/nodejs/release-keys/main/keys/4ED778F539E3634C779C87C6D7062848A1AB005C.asc)
+  - convert keys to PEM (https://stackoverflow.com/questions/10966256/erlang-importing-gpg-public-key)
+  - check signature of the checksum file with each key until there's a match
+  - match the hash for the archive filename
+  - check integrity of the downloaded archive
+  - return the archive
+
+  sigh ... why make it simple?
+  """
+
+  require Logger
+
+  @base_url "https://nodejs.org/dist/"
+end