How to build the "dist" in Node.js project

Here is the Leaflet Routing Machine:

https://github.com/perliedman/leaflet-routing-machine

The "main" in "package.json" is "./dist/leaflet-routing-machine.js", but the real source file in the project is "src/index.js".

Here is the "package.json":https://github.com/perliedman/leaflet-routing-machine/blob/master/package.json

{"name": "leaflet-routing-machine","version": "3.2.12","description": "Routing for Leaflet","directories": {"example": "examples","dist": "dist"  },"main": "./dist/leaflet-routing-machine.js","dependencies": {"@mapbox/corslite": "0.0.7","@mapbox/polyline": "^0.2.0","osrm-text-instructions": "^0.13.2"  }}

Here is the "src/index.js":https://github.com/perliedman/leaflet-routing-machine/blob/master/src/index.js

var L = require('leaflet'),    Control = require('./control'),    Itinerary = require('./itinerary'),

I'm creating my first node.js project, I think the "main" should be like this:

"main": "src/index.js"

What command is used to build the "./dist/leaflet-routing-machine.js" in the "Leaflet Routing Machine" project?