Document 'Copy Blob from URL' size limit

Author: stilist

lib/azurex/blob.ex

@@ -169,6 +169,9 @@ defmodule Azurex.Blob do
 
   @doc """
   Copies a blob to a destination.
+  
+  Note: Azure’s ‘[Copy Blob from URL](https://learn.microsoft.com/en-us/rest/api/storageservices/copy-blob-from-url)’
+  operation has a maximum size of 256 MiB.
   """
   @spec copy_blob(String.t(), String.t(), optional_string) ::
           {:ok, HTTPoison.Response.t()} | {:error, term()}