feat: Add EmptyError

Sources/Core/Utilities/EmptyError.swift

@@ -0,0 +1,23 @@
+//
+//  EmptyError.swift
+//  RakuyoKit
+//
+//  Created by Rakuyo on 2024/5/27.
+//  Copyright © 2024 RakuyoKit. All rights reserved.
+//
+
+import Foundation
+
+public typealias NoErrorResult<Success> = Result<Success, EmptyError>
+
+// MARK: - EmptyError
+
+/// Placeholder when `.failure` is needed but `Error` is not needed
+///
+/// `Result<Success, Never>` means no error will occur, so `.failure` cannot be constructed in this case
+/// But sometimes `.failure` is needed but it doesn't matter what kind of error is thrown.
+/// It would be troublesome to construct a specific Error in this case. In this case, `EmptyError` can be used
+public struct EmptyError: Error, ExpressibleByNilLiteral {
+    public init() { }
+    public init(nilLiteral _: ()) { }
+}