Add script to run the correct invocations of swift format

Scripts/format.sh

@@ -0,0 +1,20 @@
+#!/bin/sh
+##===----------------------------------------------------------------------===##
+##
+## This source file is part of the Swift Argument Parser open source project
+##
+## Copyright (c) 2025 Apple Inc. and the Swift project authors
+## Licensed under Apache License v2.0 with Runtime Library Exception
+##
+## See https://swift.org/LICENSE.txt for license information
+##
+##===----------------------------------------------------------------------===##
+
+# Move to the project root
+cd "$(dirname "$0")" || exit
+cd ..
+echo "Formatting Swift sources in $(pwd)"
+
+# Run the format / lint commands
+git ls-files -z '*.swift' | xargs -0 swift format format --parallel --in-place
+git ls-files -z '*.swift' | xargs -0 swift format lint --strict --parallel