TypeScript Support

[marklundin]

This PR adds support for declaring script attribute via TypeScript. Tests included

import { Script } from 'playcanvas'

export class My extends Script {
  /** @attribute */
  num : Number = 10

  /** @attribute */
  str : String = 'hello'
} 

It also adds supports for declaring enums and interfaces

import { Script } from 'playcanvas'

enum Options { OFF, ON, UNKNOWN }

interface Enemy {
  speed : Number
  boost: Boolean
}

export class My extends Script {
  /** @attribute */
  opts : Options
  
  /** @attribute */
  enemies : Enemy[]
}