OTA Updater for micropython running on a Pico W

• Based on Kevin McAleer's MicroPython Over-the-Air updater modified as follows:
  • The WiFi connection is made outside of OTAUpdater
  • Allows multiple files to be specified for updating, using this syntax:

    # Check for OTA updates
    firmware_url = f"https://github.com/{GitHub_username}/{repo_name}/{branch}/"
    ota_updater = OTAUpdater(firmware_url, <filename1>, <filename2>, ...)
    ota_updater.download_and_install_update_if_available()