docs: update Package.swift with updated SPM spec (awslabs#645)

Author: Ganesh Jangir

Package.swift

@@ -48,12 +48,12 @@ import struct Foundation.URL
         name: "YourNameHere",
         platforms: [.macOS(.v10_15), .iOS(.v13)],
         dependencies: [
-            .package(name: "AWSSwiftSDK", path: "/Users/<YourUserName>/Projects/Amplify/SwiftSDK/aws-sdk-swift")
+            .package(path: "/Users/<YourUserName>/Projects/Amplify/SwiftSDK/aws-sdk-swift")
         ],
         targets: [
              .target(
                  name: "YourNameHere",
-                 dependencies: [.product(name: "S3", package: "AWSSwiftSDK")])
+                 dependencies: [.product(name: "AWSS3", package: "aws-sdk-swift")])
         ]
      )
 */

README.md

@@ -80,14 +80,14 @@ let package = Package(
     name: "TestSdk",
     platforms: [.macOS(.v10_15), .iOS(.v13)],
     dependencies: [
-        .package(name: "AWSSwiftSDK", url: "https://github.com/awslabs/aws-sdk-swift", from: "0.1.0"),
+        .package(url: "https://github.com/awslabs/aws-sdk-swift", from: "0.1.0"),
     ],
     targets: [
         // Targets are the basic building blocks of a package. A target can define a module or a test suite.
         // Targets can depend on other targets in this package, and on products in packages this package depends on.
         .target(
             name: "TestSdk",
-            dependencies: [.product(name: "AWSCognitoIdentity", package: "AWSSwiftSDK")]),
+            dependencies: [.product(name: "AWSCognitoIdentity", package: "aws-sdk-swift")]),
         .testTarget(
             name: "TestSdkTests",
             dependencies: ["TestSdk"]),