Examples: Add a Hello World example (#1)

### Motivation

Having a simple "getting started" example is helpful for new users.

### Modifications

Adds the first example, using Vapor, and links it into the documentation.

### Result

New users can start from a tested starting point.

### Test Plan

Built and deployed the example locally, and ran the soundness checks.

Author: euanh

Examples/HelloWorldVapor/.gitignore

@@ -0,0 +1,8 @@
+.DS_Store
+/.build
+/Packages
+xcuserdata/
+DerivedData/
+.swiftpm/configuration/registries.json
+.swiftpm/xcode/package.xcworkspace/contents.xcworkspacedata
+.netrc

Examples/HelloWorldVapor/Package.resolved

@@ -0,0 +1,27 @@
+// swift-tools-version: 6.0
+
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftContainerPlugin open source project
+//
+// Copyright (c) 2024 Apple Inc. and the SwiftContainerPlugin project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftContainerPlugin project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import PackageDescription
+
+let package = Package(
+    name: "hello-world",
+    platforms: [.macOS(.v13)],
+    dependencies: [
+        .package(url: "https://github.com/vapor/vapor", .upToNextMajor(from: "4.102.0")),
+        .package(url: "https://github.com/apple/swift-container-plugin", from: "0.1.0"),
+    ],
+    targets: [.executableTarget(name: "hello-world", dependencies: [.product(name: "Vapor", package: "vapor")])]
+)

Examples/HelloWorldVapor/Package.swift

@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftContainerPlugin open source project
+//
+// Copyright (c) 2024 Apple Inc. and the SwiftContainerPlugin project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftContainerPlugin project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import Foundation
+import Vapor
+
+let myos = ProcessInfo.processInfo.operatingSystemVersionString
+
+let app = try Application(.detect())
+app.http.server.configuration.hostname = "0.0.0.0"
+defer { app.shutdown() }
+
+app.get { _ in "Hello World, from \(myos)\n" }
+
+try app.run()

Examples/HelloWorldVapor/Sources/main.swift

@@ -47,3 +47,5 @@ Trying to pull registry.example.com/myservice@sha256:a3f75d0932d052dd9d448a1c904
 Swift Container Plugin requires Swift 6.0 and runs on macOS and Linux.   It does not require a local container runtime to be installed in order to build an image.
 
 Learn more about setting up your project in the [ContainerImageBuilder plugin documentation](Sources/ContainerImageBuilderPluginDocumentation/Documentation.docc/ContainerImageBuilderPlugin.md).
+
+Take a look at the [Examples](Examples).

README.md

@@ -18,6 +18,8 @@ The ContainerImageBuilder plugin is a Swift Package Manager command plugin which
 The plugin requires Swift 6.0 and runs on macOS and Linux.
 The plugin does not require a container runtime to be installed locally in order to build an image.
 
+Try one of the [Examples](../../../Examples)
+
 ## Install a Swift SDK for cross-compilation on macOS
 
 If you are running on macOS, you can use a [Swift SDK](https://github.com/apple/swift-evolution/blob/main/proposals/0387-cross-compilation-destinations.md) to cross-compile your server executable for Linux.   Either:
@@ -29,7 +31,7 @@ Check that the SDK is available.   In this case we have installed the Swift Stat
 
 ```shell
 % swift sdk list
-swift-6.0-DEVELOPMENT-SNAPSHOT-2024-07-02-a_static-linux-0.0.1
+swift-6.0.1-RELEASE_static-linux-0.0.1
 ```
 
 > Note: To use the Static Linux SDK on macOS, you must [install the open source Swift toolchain from swift.org](https://www.swift.org/documentation/articles/static-linux-getting-started.html#installing-the-sdk)