clear abstract method

Clears the buffer of any key codes.

This method should be called at the end of each frame to ensure that the buffer is up-to-date:

while (true) {
  // Process keys.
  const qKey = 0x51;
  if (bufferedKeys.isPressed(qKey)) {
    break;
  }
  // Clear the buffer.
  await bufferedKeys.clear();

  // Render the frame.
  // ...
}