Add :logger to :extra_applications

[wojtekmach]

I noticed a bunch of warnings when running:

$ mix archive.install github hexpm/hex branch main

which look like this:

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

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

  2. If :logger 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 :logger, you may optionally skip this warning by adding [xref: [exclude: [Logger]]] to your "def project" in mix.exs

Here are all the locations we use Logger:

lib/hex/parallel.ex:79: Hex.Parallel.handle_info/2
lib/hex/parallel.ex:88: Hex.Parallel.handle_info/2
lib/hex/remote_converger.ex:82: Hex.RemoteConverger.run_solver/5
lib/hex/remote_converger.ex:83: Hex.RemoteConverger.run_solver/5
lib/hex/remote_converger.ex:95: Hex.RemoteConverger.run_solver/5
lib/hex/solver/solver.ex:147: Hex.Solver.Solver.choose_package_version/1
lib/hex/solver/solver.ex:165: Hex.Solver.Solver.add_incompatibility/2
lib/hex/solver/solver.ex:190: Hex.Solver.Solver.conflict_resolution/2
lib/hex/solver/solver.ex:313: Hex.Solver.Solver.do_conflict_resolution/3
lib/hex/solver/solver.ex:97: Hex.Solver.Solver.propagate_incompatibility/4

Since we depend on Elixir 1.5, it is safe to use :extra_applications.