Particle sample of Three.js requires ES6 module version of SPE.js

[cx20]

I updated the Three.js sample to ES6 version.
However, the SPE.js used does not support the ES6 module, so the Particle sample cannot represent smoke.

https://cx20.github.io/webgl-test/examples/threejs/complex/index.html

[cx20]

I tentatively used the fork version of SPE.js to get the sample working.
#71

However, since it is not an ES6 module version, it will not work after a few months.