Add Discogs function to fetch artist image

lib/discogs.ex

@@ -7,5 +7,11 @@ defmodule Discogs do
     API.get_artist(id, discogs_config)
   end
 
+  def get_artist_image(url) do
+    discogs_config = discogs_config()
+
+    API.get_artist_image(url, discogs_config)
+  end
+
   defp discogs_config, do: Discogs.Config.resolve(:music_library)
 end