Make JSONEncoder & JSONDecoder internal

to avoid name collisions when using XXClient library

Sources/XXClient/Helpers/JSONDecoder.swift

 import CustomDump
 import Foundation
 
-public class JSONDecoder: Foundation.JSONDecoder {
-  public override init() {
+class JSONDecoder: Foundation.JSONDecoder {
+  override init() {
     super.init()
   }
 
-  public override func decode<T>(_ type: T.Type, from data: Data) throws -> T where T: Decodable {
+  override func decode<T>(_ type: T.Type, from data: Data) throws -> T where T: Decodable {
     do {
       let data = convertNumberToString(in: data, at: "Value")
       return try super.decode(type, from: data)

Sources/XXClient/Helpers/JSONEncoder.swift

 import CustomDump
 import Foundation
 
-public class JSONEncoder: Foundation.JSONEncoder {
-  public override init() {
+class JSONEncoder: Foundation.JSONEncoder {
+  override init() {
     super.init()
   }
 
-  public override func encode<T>(_ value: T) throws -> Data where T: Encodable {
+  override func encode<T>(_ value: T) throws -> Data where T: Encodable {
     do {
       var data = try super.encode(value)
       data = convertStringToNumber(in: data, at: "Value")