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/Tasks/CreateRootFolderTask.swift

@@ -0,0 +1,48 @@
+import Foundation
+
+public struct CreateRootFolderTask {
+    
+    // MARK: Properties
+    
+    private let fileService: FileServicing
+    
+    // MARK: Initialisers
+    
+    public init(fileService: FileServicing) {
+        self.fileService = fileService
+    }
+    
+    // MARK: Functions
+    
+    public func callAsFunction(
+        name: String,
+        at location: URL? = nil
+    ) async throws -> URL {
+        guard !name.isEmpty else {
+            throw CreateRootFolderError.nameIsEmpty
+        }
+
+        let rootFolder = if let location {
+            location
+        } else {
+            await fileService.currentFolder
+        }
+        
+        let newFolder = if #available(macOS 13.0, *) {
+            rootFolder.appending(path: name)
+        } else {
+            rootFolder.appendingPathComponent(name)
+        }
+
+        try await fileService.createFolder(at: newFolder)
+        
+        return newFolder
+    }
+    
+}
+
+// MARK: - Errors
+
+public enum CreateRootFolderError: Error {
+    case nameIsEmpty
+}