I am interested in the particle system, but only seem to be able to add that extension in Native Platform. Is there an alternative that I could use if I make a game in Web Platform?
Not for now. 
You could try creating “particle” sprites (game objects) at specific points that move/scale away, etc. I dunno about performance of this solution (or rather workaround) though.
I had thought of that but figured it would eat up system resources of mobile devices. I dunno. I might give it a try.