Scala Native 0.5 and other upgrades

[keynmol]

Hello 👋

Glad I remembered about this library. I'm building a CLI with Scala Native and thought I'd give it a go. It works, that's great!

This PR bumps SN to 0.5, and simplifies the tests to not use Cats Effect (which is not yet published for 0.5).

Please let me know if you are willing to release a new version with these changes, and if not, I can fork the project. Thanks again for your work.

---

I've been using it generically along with my project decline-derive to add completions to any command:

case class PrintCompletions(value: String)

given withCompletions[T](using
    t: CommandApplication[T]
): CommandApplication[T | PrintCompletions] =
  new:
    val newSubcommands =
      val bash =
        Command("bash", "output autocompletion script for bash")(
          Opts(
            PrintCompletions(Completion.bashCompletion(command))
          )
        )

      val zsh = Command("zsh", "output autocompletion script for zsh")(
        Opts(
          PrintCompletions(Completion.zshBashcompatCompletion(command))
        )
      )

      val completion = Command(
        "completion",
        "output autocompletion scripts for common shells"
      ) {
        Opts.subcommands(bash, zsh)
      }

      t.subcommands :+ completion
    end newSubcommands

    override def command: Command[T | PrintCompletions] =
      Command[T | PrintCompletions](t.command.name, t.command.header)(
        Opts.subcommands(newSubcommands.head, newSubcommands.tail*)
      )
    override def subcommands: List[Command[T | PrintCompletions]] =
      newSubcommands

And then at usage site:

        CommandApplication.parseOrExit[CLI | PrintCompletions](args) match
          case PrintCompletions(value) => print(value)
          case cli: CLI.New            => commandNew(context, cli)

It works great!

[keynmol]

I was getting weird compilation errors because of implicit root project being created, but without dependencies