Add :crypto to :extra_applications

[brettbeatty]

Installing project as an archive emits this warning:

warning: :crypto.strong_rand_bytes/1 defined in application :crypto is used by the current application but the current application does not depend on :crypto. To fix this, you must do one of:

  1. If :crypto is part of Erlang/Elixir, you must include it under :extra_applications inside "def application" in your mix.exs

  2. If :crypto is a dependency, make sure it is listed under "def deps" in your mix.exs

  3. In case you don't want to add a requirement to :crypto, you may optionally skip this warning by adding [xref: [exclude: [:crypto]]] to your "def project" in mix.exs

  lib/mix/tasks/deps.try.ex:51: Mix.Tasks.Deps.Try.generate_tag/0

:crypto is a part of Erlang, so it should be included under :extra_applications in mix.exs