Add Swift 5.8 support

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.7
+// swift-tools-version:5.8
 // The swift-tools-version declares the minimum version of Swift required to build this package.
 
 import PackageDescription

Package@swift-5.7.swift

@@ -0,0 +1,41 @@
+// swift-tools-version:5.7
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+import Foundation
+
+let package = Package(
+    name: "swift-filestreamer",
+    platforms: [
+        .macOS(.v10_13),
+        .iOS(.v11),
+        .tvOS(.v11),
+        .watchOS(.v4),
+    ],
+    products: [
+        // Products define the executables and libraries a package produces, and make them visible to other packages.
+        .library(
+            name: "FileStreamer",
+            targets: ["FileStreamer"]),
+    ],
+    dependencies: [
+        // Dependencies declare other packages that this package depends on.
+        .package(url: "https://github.com/apple/swift-system.git", from: "1.0.0"),
+    ],
+    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: "FileStreamer",
+            dependencies: [
+                .product(name: "SystemPackage", package: "swift-system"),
+            ]),
+        .testTarget(
+            name: "FileStreamerTests",
+            dependencies: ["FileStreamer"]),
+    ]
+)
+
+if ProcessInfo.processInfo.environment["ENABLE_DOCC_SUPPORT"] == "1" {
+    package.dependencies.append(.package(url: "https://github.com/apple/swift-docc-plugin", from: "1.0.0"))
+}