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/Protocols/FileServicing.swift

@@ -0,0 +1,25 @@
+import Foundation
+
+public protocol FileServicing {
+    
+    // MARK: Computed
+    
+    var currentFolder: URL { get async }
+    
+    // MARK: Functions
+    
+    func createFolder(at url: URL) async throws (FileServiceError)
+    func delete(at url: URL) async throws (FileServiceError)
+    func exists(at url: URL) async throws (FileServiceError) -> Bool
+    
+}
+
+// MARK: - Errors
+
+public enum FileServiceError: Error, Equatable {
+    case folderNotCreated
+    case urlAlreadyExists
+    case urlNotDeleted
+    case urlNotExists
+    case urlNotFileURL
+}