Creating the Guides

line-chart.diff

import React from 'react';
import PropTypes from 'prop-types';

const LineChart = ({ data }) => {
...
  return (
    <svg viewBox={`0 0 ${chartWidth} ${chartHeight}`} role="presentation">
       ...
+      {guides.map((_, index) => {
+        const ratio = index / guides.length;
+        const y = chartHeight - paddingY - chartHeight * ratio;
+
+        return <polyline key={index} className="stroke-gray-200" fill="none" strokeWidth={1} points={`${paddingX / 2},${y} ${chartWidth - paddingX / 2},${y}`} />;
+      })}
       ...
    </svg>
  );
};

export default LineChart;