[CI] Add support for GitHub Actions

Author: shahmishal

.github/workflows/pull_request.yml

@@ -0,0 +1,18 @@
+name: Pull request
+
+on:
+  pull_request:
+    types: [opened, reopened, synchronize]
+
+jobs:
+  tests:
+    name: Test
+    uses: swiftlang/github-workflows/.github/workflows/swift_package_test.yml@main
+    with:
+      linux_build_command: "cd Guest && ./build.sh"
+      enable_windows_checks: false
+  soundness:
+    name: Soundness
+    uses: swiftlang/github-workflows/.github/workflows/soundness.yml@main
+    with:
+      license_header_check_project_name: "Swift"

.license_header_template

@@ -0,0 +1,11 @@
+@@===----------------------------------------------------------------------===@@
+@@
+@@ This source file is part of the Swift 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
+@@ See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+@@
+@@===----------------------------------------------------------------------===@@