I am currently making a conference call in which two participants join via SDK.One participant initiates a call from react-native and other joins the call via push notification which says "hey a talker is waiting for you in the conference" in react-native app.

And on the backend, I am using node js which is sending Twilio the twiml response like this

const voiceResponse = new twilio.twiml.VoiceResponse();
voiceResponse.pause({length: 1});
voiceResponse.say('Hello. Your call is starting now.');
const dial = voiceResponse.dial();
dial.conference(
  {
    endConferenceOnExit: true,
    record: 'record-from-start',
    recordingStatusCallback: `${process.env.HOST}/v1/twilio/recording`,
    trim: 'do-not-trim',
    statusCallback: `${process.env.HOST}/v1/twilio/status`,
    statusCallbackEvent: 'start end join leave mute hold speaker',
  },
  req.body.conversation_id,
);

Now I want to join a participant in a conference via PSTN, how it can be done?