Add sample script

Author: giginet

Example/.gitignore

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+.DS_Store
+/.build
+/Packages
+/*.xcodeproj

Example/Package.resolved

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+// swift-tools-version:4.2
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "Example",
+    dependencies: [
+        .package(path: "../"),
+    ],
+    targets: [
+        .target(
+            name: "Example",
+            dependencies: ["AWSLambdaRuntime"]),
+    ]
+)

Example/Package.swift

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+# Example
+
+A description of this package.

Example/README.md

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+import Foundation
+import AWSLambdaRuntime
+
+struct User: Decodable {
+    let firstName: String
+}
+
+enum GreetingError: String, LambdaError {
+    var message: String {
+        switch self {
+        case .invalidPayload:
+            return "Payload is invalid"
+        }
+    }
+    
+    case invalidPayload
+}
+
+run { context -> Result<GreetingError> in
+    guard let data = context.payload,
+        let user = try? JSONDecoder().decode(User.self, from: data) else {
+        return .failure(error: .invalidPayload)
+    }
+    let payload = try! JSONSerialization.data(withJSONObject: ["message": "Hello \(user.firstName)"])
+    return .success(payload: payload, contentType: "application/json")
+}