ESP01 sketch taking HTTPS GET URLs from Pico over serial, returning response to Pico

SerialHttpsClient.ino

#include <Arduino.h>

#include <ESP8266WiFi.h>
#include <ESP8266WiFiMulti.h>

#include <ESP8266HTTPClient.h>

#include <WiFiClientSecureBearSSL.h>

ESP8266WiFiMulti WiFiMulti;

void setup() {
  Serial.begin(115200);

  WiFi.mode(WIFI_STA);
  WiFiMulti.addAP("ssid", "password");
}

void loop() {
  if ((WiFiMulti.run() == WL_CONNECTED)) {

    std::unique_ptr<BearSSL::WiFiClientSecure>client(new BearSSL::WiFiClientSecure);

    client->setInsecure();   // client->setFingerprint(fingerprint);
    
    HTTPClient https;

    String url = Serial.readStringUntil('\n');

    if (url.length()>1)
    {
      if (https.begin(*client, url)) {

        int httpCode = https.GET();

        if ((httpCode > 0) &&
            (httpCode == HTTP_CODE_OK || httpCode == HTTP_CODE_MOVED_PERMANENTLY)) {
          Serial.println(https.getString());
        }
        else {
          Serial.println();
        }

        https.end();
      } else {
        Serial.println();
      }
    }
  }
}

Just connect Pico 3V3/GND/GP0/GP1/3V3 to ESP01 3V3/GND/RX/TX/EN.

Allows Pico HTTPS GET internet access through the ESP01:
https://www.raspberrypi.org/forums/viewtopic.php?f=146&t=307704#p1840946

Now works with Pico C-SDK as well:
https://github.com/Hermann-SW/C-SDK_HTTPS_GET_through_ESP01#c-sdk-https-get-through-esp01-wifi