#include <ArduinoJson.h>

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  char input[] = "{\"recenttracks\":{\"track\":{\"image\": \"url\"}}}";
  DynamicJsonDocument doc(200);
  DeserializationError error = deserializeJson(doc, input);
  if (error) {
    Serial.print("deserializeJson() failed for LastFM: ");
    Serial.println(error.c_str());
  }
  JsonObject parsed = doc["recenttracks"]["track"];
  serializeJson(parsed["image"], Serial);
}

void loop() {
  // put your main code here, to run repeatedly:

}