FEATURE: Add concept of enum values to language core

[grebaldi]

Declaration:

export enum HeadlineVariant {
  REGULAR({
    className: "text-xl text-gray"
  })
  CTA({
    className: "text-xxl text-red"
  })
}

Usage:

export component Headline {
  variant: HeadlineVariant
  text: string

  return <h1 className={variant.className}>{text}</h1>
}