Loading a module with plain javascript is not working

I am importing a module with plain js file like so:

import * as Highcharts from 'highcharts';

Highcharts.chart('container', {

    title: {
        text: 'Solar Employment Growth by Sector, 2010-2016'
    },

    subtitle: {
        text: 'Source: thesolarfoundation.com'
    },

    yAxis: {
        title: {
            text: 'Number of Employees'
        }
    },

    xAxis: {
        accessibility: {
            rangeDescription: 'Range: 2010 to 2017'
        }
    },

    legend: {
        layout: 'vertical',
        align: 'right',
        verticalAlign: 'middle'
    },

    plotOptions: {
        series: {
            label: {
                connectorAllowed: false
            },
            pointStart: 2010
        }
    },

    series: [{
        name: 'Installation',
        data: [43934, 52503, 57177, 69658, 97031, 119931, 137133, 154175]
    }, {
        name: 'Manufacturing',
        data: [24916, 24064, 29742, 29851, 32490, 30282, 38121, 40434]
    }, {
        name: 'Sales & Distribution',
        data: [11744, 17722, 16005, 19771, 20185, 24377, 32147, 39387]
    }, {
        name: 'Project Development',
        data: [null, null, 7988, 12169, 15112, 22452, 34400, 34227]
    }, {
        name: 'Other',
        data: [12908, 5948, 8105, 11248, 8989, 11816, 18274, 18111]
    }],

    responsive: {
        rules: [{
            condition: {
                maxWidth: 500
            },
            chartOptions: {
                legend: {
                    layout: 'horizontal',
                    align: 'center',
                    verticalAlign: 'bottom'
                }
            }
        }]
    }

});

and imported to index.html file as module like this:

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <figure>
        <div id="container"></div>
    </figure>
    <script type="module" src="./index.js"></script>
</body>

</html>

but the Higcharts not available with my browser. getting error as:

Failed to resolve module specifier "highcharts". Relative references must start with either "/", "./", or "../".

how to import modules in plain js files?