Update Package.swift (#722)

Fix to resolve linker error in xcode because of missing import.  #721

Author: nishant-dani

Package.swift

@@ -38,6 +38,7 @@ let package = Package(
             dependencies: [
                 .target(name: "CAsyncHTTPClient"),
                 .product(name: "NIO", package: "swift-nio"),
+                .product(name: "NIOTLS", package: "swift-nio"),
                 .product(name: "NIOCore", package: "swift-nio"),
                 .product(name: "NIOPosix", package: "swift-nio"),
                 .product(name: "NIOHTTP1", package: "swift-nio"),
@@ -56,6 +57,7 @@ let package = Package(
             name: "AsyncHTTPClientTests",
             dependencies: [
                 .target(name: "AsyncHTTPClient"),
+                .product(name: "NIOTLS", package: "swift-nio"),
                 .product(name: "NIOCore", package: "swift-nio"),
                 .product(name: "NIOConcurrencyHelpers", package: "swift-nio"),
                 .product(name: "NIOEmbedded", package: "swift-nio"),