Is your feature request related to a problem? Please describe.
I'm attempting to integrate APNSwift into my Vapor project, and my app follows a pattern where I store dependencies in a StorageKey. Due to this conformance, the type being added to the StorageKey must be marked Sendable.

public protocol StorageKey { /// The type of the stored value associated with this key type. associatedtype Value: Sendable }

Describe the solution you'd like
I noticed this extension already exists, and both JSONEncoder and JSONDecoder are marked as @unchecked Sendable in Apple's frameworks, so assuming this is possible to do in APNSwift it should be a quick improvement.

extension APNSClient: Sendable where Decoder: Sendable, Encoder: Sendable {}

Describe alternatives you've considered
I started by making my own @unchecked Sendable wrapper before noticing that conformance already existed. I don't really find much value from it and it's kind of an ugly solution, but I could always fall back to it if needed.

final class SendableAPNSClient: @unchecked Sendable { let client: APNSClient<JSONDecoder, JSONEncoder> private init(client: APNSClient<JSONDecoder, JSONEncoder>) { self.client = client } }

Additional context
Not much really, except to say that so far using the project has been a delight so thank you very much for that!