Callback for when `autoload = true` but there is no applicable session to load

[mrjones2014]

Use case: I have autoload = true in persisted.nvim, as well as a custom, bespoke startup screen (not using any plugin) in my config, but I only want to show the startup screen if persisted.nvim is not going to load a session.

Maybe an API like:

require('persisted').setup({
  autoload = true,
  on_no_session_to_autoload = function()
    -- load my custom startup screen
  end
})