懒惰的值序列化

Hi, for example, I want to send a JPEG image from the ESP32 camera (through MQTT, for example) using JSON, so I need to encode the JPEG data as base64. And its memory space stores the JPEG in memory again, even larger, because it is encoded as base64. So I patched the ArduinoJson library to do it incrementally. I created an Abstract class DynamicData.