Enum constants not evaluated

The following `ambient` member is not parsed as an attribute, nor is an error raised

```javascript
import { Script } from 'playcanvas'

/** @enum {number} */
const Lights = {
    ON: 1,
    OFF: 0,
    UNKNOWN: 0.5
}

class Hack extends Script {
    /**
     * @attribute
     * @type {Lights}
     */
    ambient = Lights.OFF
}

export { Hack };
```