Fix up license headers and enable check (#746)

Author: natecook1000

.github/workflows/pull_request.yml

@@ -53,6 +53,5 @@ jobs:
     name: Soundness
     uses: swiftlang/github-workflows/.github/workflows/soundness.yml@main
     with:
-      license_header_check_enabled: false  # feature: https://github.com/swiftlang/github-workflows/issues/78
       license_header_check_project_name: "Swift Argument Parser"  # bug: https://github.com/swiftlang/github-workflows/issues/76
       shell_check_enabled: false  # bug: https://github.com/apple/swift-argument-parser/issues/703

.license_header_template

@@ -0,0 +1,10 @@
+@@===----------------------------------------------------------------------===@@
+@@
+@@ This source file is part of the Swift Argument Parser open source project
+@@
+@@ Copyright (c) YEARS 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
+@@
+@@===----------------------------------------------------------------------===@@

.licenseignore

@@ -0,0 +1,29 @@
+.gitignore
+**/.gitignore
+.licenseignore
+.gitattributes
+.git-blame-ignore-revs
+.mailfilter
+.mailmap
+.spi.yml
+.swift-format
+.editorconfig
+.github/*
+*.md
+*.mdoc
+*.txt
+*.yml
+*.yaml
+*.json
+*.png
+*.bash
+*.cmake
+*.cmake.in
+Package.swift
+**/Package.swift
+Package@*.swift
+**/Package@*.swift
+Package.resolved
+**/Package.resolved
+.unacceptablelanguageignore
+**/Snapshots/*

Examples/color/Color.swift

@@ -1,12 +1,11 @@
 //===----------------------------------------------------------------------===//
 //
-// This source file is part of the Swift.org open source project
+// This source file is part of the Swift Argument Parser open source project
 //
 // Copyright (c) 2024 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
-// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
 //
 //===----------------------------------------------------------------------===//
 

Examples/count-lines/CountLines.swift

@@ -1,4 +1,4 @@
-//===----------------------------------------------------------*- swift -*-===//
+//===----------------------------------------------------------------------===//
 //
 // This source file is part of the Swift Argument Parser open source project
 //

Examples/math/Math.swift

@@ -1,4 +1,4 @@
-//===----------------------------------------------------------*- swift -*-===//
+//===----------------------------------------------------------------------===//
 //
 // This source file is part of the Swift Argument Parser open source project
 //

Examples/repeat/Repeat.swift

@@ -1,4 +1,4 @@
-//===----------------------------------------------------------*- swift -*-===//
+//===----------------------------------------------------------------------===//
 //
 // This source file is part of the Swift Argument Parser open source project
 //

Examples/roll/SplitMix64.swift

@@ -1,4 +1,4 @@
-//===----------------------------------------------------------*- swift -*-===//
+//===----------------------------------------------------------------------===//
 //
 // This source file is part of the Swift Argument Parser open source project
 //

Examples/roll/main.swift

@@ -1,4 +1,4 @@
-//===----------------------------------------------------------*- swift -*-===//
+//===----------------------------------------------------------------------===//
 //
 // This source file is part of the Swift Argument Parser open source project
 //

Package.swift

@@ -1,5 +1,5 @@
 // swift-tools-version:5.7
-//===----------------------------------------------------------*- swift -*-===//
+//===----------------------------------------------------------------------===//
 //
 // This source file is part of the Swift Argument Parser open source project
 //