Updated SunLight as a class to use the latest versions of three.js

[forerunrun]

Updates:

• SunLight.js is now an es6 module class that imports the latest versions of three.js with the latest syntax usage of the three.js library.
• example-scene.js is now a module type script that imports dependencies internally from both three.js and SunLight.js.
• index.html is updated with references to three.js through importmaps, example-scene.js is now the only file referenced on the dom where all other scripts are imported.