Root folder creation (#2)

This PR contains the work done to create the root folder of a new project when executing the _colibri_ executable. In addition, some other work has been done:

* added the `ArgumentParser` package dependency to the package;
* implemented the `FileService` service in the _library_ target;
* implemented the `CreateRootFolderTask` task in the _library_ target;
* removed some unnecessary comments and boilerplate code;

Reviewed-on: #2
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

Sources/Library/Services/FileService.swift

@@ -0,0 +1,78 @@
+import Foundation
+
+public struct FileService: FileServicing {
+
+    // MARK: Properties
+    
+    private let fileManager: FileManager
+    
+    // MARK: Initialisers
+    
+    public init(fileManager: FileManager = .default) {
+        self.fileManager = fileManager
+    }
+    
+    // MARK: Computed
+    
+    public var currentFolder: URL {
+        get async {
+            .init(at: fileManager.currentDirectoryPath)
+        }
+    }
+    
+    // MARK: Functions
+
+    public func createFolder(at url: URL) async throws (FileServiceError) {
+        guard try await !exists(at: url) else {
+            throw FileServiceError.urlAlreadyExists
+        }
+        
+        do {
+            try fileManager.createDirectory(
+                at: url,
+                withIntermediateDirectories: true
+            )
+        } catch {
+            throw FileServiceError.folderNotCreated
+        }
+    }
+    
+    public func delete(at url: URL) async throws (FileServiceError) {
+        guard try await exists(at: url) else {
+            throw FileServiceError.urlNotExists
+        }
+        
+        do {
+            try fileManager.removeItem(at: url)
+        } catch {
+            throw FileServiceError.urlNotDeleted
+        }
+    }
+    
+    public func exists(at url: URL) async throws (FileServiceError) -> Bool {
+        guard url.isFileURL else {
+            throw FileServiceError.urlNotFileURL
+        }
+        
+        let filePath = getPath(for: url)
+        
+        return fileManager.fileExists(atPath: filePath)
+    }
+    
+}
+
+// MARK: - Helpers
+
+private extension FileService {
+    
+    // MARK: Functions
+    
+    func getPath(for url: URL) -> String {
+        if #available(macOS 13.0, *) {
+            return url.path()
+        } else {
+            return url.path
+        }
+    }
+    
+}