Support passing arguments to async main

Sources/ArgumentParser/Parsable Types/AsyncParsableCommand.swift

@@ -25,14 +25,18 @@ public protocol AsyncParsableCommand: ParsableCommand {
 
 @available(macOS 10.15, macCatalyst 13, iOS 13, tvOS 13, watchOS 6, *)
 extension AsyncParsableCommand {
-  /// Executes this command, or one of its subcommands, with the program's
-  /// command-line arguments.
+  /// Executes this command, or one of its subcommands, with the given arguments.
   ///
-  /// Instead of calling this method directly, you can add `@main` to the root
-  /// command for your command-line tool.
-  public static func main() async {
+  /// This method parses an instance of this type, one of its subcommands, or
+  /// another built-in `AsyncParsableCommand` type, from command-line
+  /// (or provided) arguments, and then calls its `run()` method, exiting
+  /// with a relevant error message if necessary.
+  ///
+  /// - Parameter arguments: An array of arguments to use for parsing. If
+  ///   `arguments` is `nil`, this uses the program's command-line arguments.
+  public static func main(_ arguments: [String]?) async {
     do {
-      var command = try parseAsRoot()
+      var command = try parseAsRoot(arguments)
       if var asyncCommand = command as? AsyncParsableCommand {
         try await asyncCommand.run()
       } else {
@@ -42,6 +46,20 @@ extension AsyncParsableCommand {
       exit(withError: error)
     }
   }
+
+  /// Executes this command, or one of its subcommands, with the program's
+  /// command-line arguments.
+  ///
+  /// Instead of calling this method directly, you can add `@main` to the root
+  /// command for your command-line tool.
+  ///
+  /// This method parses an instance of this type, one of its subcommands, or
+  /// another built-in `AsyncParsableCommand` type, from command-line arguments,
+  /// and then calls its `run()` method, exiting with a relevant error message
+  /// if necessary.
+  public static func main() async {
+    await self.main(nil)
+  }
 }
 
 /// A type that can designate an `AsyncParsableCommand` as the program's