Rename main.swift to MarkdownCommand.swift and add @main (#10)

* Rename main.swift to MarkdownCommand.swift and add @main

* Update swift-tool-version to 5.5

* Update README.md

Author: Kyle-Ye

Package.swift

@@ -1,10 +1,8 @@
-// swift-tools-version:5.3
-// In order to support users running on the latest Xcodes, please ensure that
-// Package@swift-5.5.swift is kept in sync with this file.
+// swift-tools-version:5.5
 /*
  This source file is part of the Swift.org open source project
 
- Copyright (c) 2021 Apple Inc. and the Swift project authors
+ Copyright (c) 2021-2023 Apple Inc. and the Swift project authors
  Licensed under Apache License v2.0 with Runtime Library Exception
 
  See https://swift.org/LICENSE.txt for license information
@@ -51,9 +49,16 @@ let package = Package(
 if ProcessInfo.processInfo.environment["SWIFTCI_USE_LOCAL_DEPS"] == nil {
     // Building standalone, so fetch all dependencies remotely.
     package.dependencies += [
-        .package(url: "https://github.com/apple/swift-cmark.git", .branch("gfm")),
-        .package(url: "https://github.com/apple/swift-argument-parser", .upToNextMinor(from: "1.0.1")),
+        .package(url: "https://github.com/apple/swift-cmark.git", branch: "gfm"),
+        .package(url: "https://github.com/apple/swift-argument-parser", from: "1.2.2"),
     ]
+    
+    // SwiftPM command plugins are only supported by Swift version 5.6 and later.
+    #if swift(>=5.6)
+    package.dependencies += [
+        .package(url: "https://github.com/apple/swift-docc-plugin", from: "1.1.0"),
+    ]
+    #endif
 } else {
     // Building in the Swift.org CI system, so rely on local versions of dependencies.
     package.dependencies += [

Package@swift-5.5.swift

@@ -11,13 +11,18 @@ The markup tree provided by this package is comprised of immutable/persistent, t
 In your `Package.swift` Swift Package Manager manifest, add the following dependency to your `dependencies` argument:
 
 ```swift
-.package(url: "https://github.com/apple/swift-markdown.git", .branch("main")),
+.package(url: "https://github.com/apple/swift-markdown.git", branch: "main"),
 ```
 
 Add the dependency to any targets you've declared in your manifest:
 
 ```swift
-.target(name: "MyTarget", dependencies: ["Markdown"]),
+.target(
+    name: "MyTarget", 
+    dependencies: [
+        .product(name: "Markdown", package: "swift-markdown"),
+    ]
+),
 ```
 
 To parse a document, use `Document(parsing:)`, supplying a `String` or `URL`:
@@ -61,4 +66,4 @@ Swift Markdown can be improved to better meet your needs.
 
 Please see the [contributing guide](https://swift.org/contributing/#contributing-code) for more information.
 
-<!-- Copyright (c) 2021-2022 Apple Inc and the Swift Project authors. All Rights Reserved. -->
+<!-- Copyright (c) 2021-2023 Apple Inc and the Swift Project authors. All Rights Reserved. -->

README.md

@@ -12,6 +12,7 @@ import ArgumentParser
 import Foundation
 import Markdown
 
+@main
 struct MarkdownCommand: ParsableCommand {
     enum Error: LocalizedError {
         case couldntDecodeInputAsUTF8
@@ -50,5 +51,3 @@ struct MarkdownCommand: ParsableCommand {
         return (stdinString, Document(parsing: stdinString, options: options))
     }
 }
-
-MarkdownCommand.main()