Adopting async/await

[corysullivan]

What are your thoughts on adding an async/await option? Would you consider a PR with sonething like the following?

@available(iOS 15, macOS 12.0, watchOS 8, tvOS 15, *)
public extension URLSession {

    func load<A>(_ e: Endpoint<A>) async throws -> A {
        let request = e.request
        let (data, resp) = try await data(for: request)
        guard let h = resp as? HTTPURLResponse else {
            throw UnknownError()
        }
        guard e.expectedStatusCode(h.statusCode) else {
            throw WrongStatusCodeError(statusCode: h.statusCode, response: h, responseBody: data)
        }
        return try e.parse(data, resp).get()
    }
}