Error when I try to render a [procedural] Skybox using Babylonjs

Question

I'm trying to implement a component library that will allow babylonjs scenes to be assembled very easily using HTML (inspired by ).

I'm implementing a and I'm trying to implement it as a procedural skybox:

The relevant code:

import * as BABYLON from 'babylonjs'
import * as MAT from 'babylonjs-materials'

// later...

  const material = new MAT.SkyMaterial('skybox', this.owner.scene)
  material.backFaceCulling = false
  this.update()
  this.skybox = BABYLON.CreateBox('skybox', { size, sideOrientation: BABYLON.Mesh.BACKSIDE }, this.owner.scene)
  this.material = material

When I run this code I get two errors and the cube does not render:

babylon.js? [sm]:1          GET http://localhost:3000/src/Shaders/sky.vertex.fx 404 (Not Found)
babylon.js? [sm]:1          GET http://localhost:3000/src/Shaders/sky.fragment.fx 404 (Not Found)

It looks like it expects another library or plugin to be loaded but I can't find any documentation indicating what to load.