[response] add missing public init

Author: pjechris

Sources/SimpleHTTP/Response/DataResponse.swift

@@ -3,6 +3,11 @@ import Foundation
 public struct URLDataResponse {
     public let data: Data
     public let response: HTTPURLResponse
+
+    public init(data: Data, response: HTTPURLResponse) {
+        self.data = data
+        self.response = response
+    }
 }
 
 extension URLDataResponse {