[CI] Add support for GitHub Actions (#1241)

* [CI] Add support for GitHub Actions

* Disable License, Docs, Format, Unacceptable Lang, and API breakage checks

* Use Docker image for Windows builds

* update the CI to only run on nightly-main

Author: shahmishal

.github/workflows/pull_request.yml

@@ -0,0 +1,24 @@
+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_swift_versions: '["nightly-main"]'
+      windows_swift_versions: '["nightly-main"]'
+
+  soundness:
+    name: Soundness
+    uses: swiftlang/github-workflows/.github/workflows/soundness.yml@main
+    with:
+      license_header_check_project_name: "Swift.org"
+      license_header_check_enabled: false
+      docs_check_enabled: false
+      format_check_enabled: false
+      unacceptable_language_check_enabled: false
+      api_breakage_check_enabled: false