How can I bias output signal in Web Audio API?

I’m trying to make some audio signals with web audio API. And I want to add some bias to my audio signal in web/js. How can I bias up/down audio signal like this image?

image from https://www.csounds.com/tootsother/east/Bias/Bias.html

I made some oscillators and I couldn’t find clues in my searching ability.

  const ac = new AudioContext();

  const leftOsc = ac.createOscillator();
  const leftGain = ac.createGain();
  const rightOsc = ac.createOscillator();
  const rightGain = ac.createGain();
  const merger = ac.createChannelMerger(2);

  leftOsc.connect(leftGain);
  leftGain.connect(merger, 0, 0);
  rightOsc.connect(rightGain);
  rightGain.connect(merger, 0, 1);

  leftOsc.type = 'sine';
  leftOsc.frequency.value = 440;
  leftGain.gain.value = 0.5;
  leftOsc.start();

  rightOsc.type = 'sine';
  rightOsc.frequency.value = 440;
  rightGain.gain.value = 0.5;
  rightOsc.start();

  merger.connect(ac.destination);