Read gauge.js and you find:
module.exports = {
Gauge: Gauge,
Donut: Donut,
BaseDonut: BaseDonut,
TextRenderer: TextRenderer
};
There are many ways of import. With import something from 'somewere' you require exports.default, but there is no default. With the brackets you required exports.Gauge.
An other way is import * as gauge from './gauge.js/dist/gauge.js', but then you have to use gauge.Gauge.