[Docs] Math operations on evaluated tokens

<!DOCTYPE html>
<html>

<head>
  <meta charset="utf-8">
  <title>ZingSoft Demo</title>

  <script nonce="undefined" src="https://cdn.zingchart.com/zingchart.min.js"></script>
  <style></style>
</head>

<body>
  <div id="myChart"></div>
  <script>
    ZC.LICENSE = ["569d52cefae586f634c54f86dc99e6a9", "b55b025e438fa8a98e32482b5f768ff5"];
    let chartConfig = {
      type: 'bar',
      plot: {
        valueBox: {
          text: 'Node Value: %v <br> Double Node Value: {{ %v * 2 }}',
          textAlign: 'left',
        },
      },
      plotarea: {
        margin: 'dynamic'
      },
      scaleX: {
        labels: ['Mon', 'Tue', 'Wed', 'Thu', 'Fri'],
      },
      series: [{
        values: [30, 34, 14, 15, 31],
        text: 'Weekly Gains',
        dataDailyName: ['Nick', 'Chris', 'Jeanette', 'Christie', 'Dave']
      }]
    };

    zingchart.render({
      id: 'myChart',
      data: chartConfig,
      height: 400,
      width: "100%"
    });
  </script>
</body>

</html>

<!DOCTYPE html>
<html>

<head>
  <meta charset="utf-8">
  <title>ZingSoft Demo</title>

  <script src="https://cdn.zingchart.com/zingchart.min.js"></script>
</head>

<body>
  <div id="myChart"></div>
</body>

</html>

let chartConfig = {
  type: 'bar',
  plot: {
    valueBox: {
      text: 'Node Value: %v <br> Double Node Value: {{ %v * 2 }}',
      textAlign: 'left',
    },
  },
  plotarea: {
    margin: 'dynamic'
  },
  scaleX: {
    labels: ['Mon', 'Tue', 'Wed', 'Thu', 'Fri'],
  },
  series: [{
    values: [30, 34, 14, 15, 31],
    text: 'Weekly Gains',
    dataDailyName: ['Nick', 'Chris', 'Jeanette', 'Christie', 'Dave']
  }]
};

zingchart.render({
  id: 'myChart',
  data: chartConfig,
  height: 400,
  width: "100%"
});