please document Class-Style Vue Components

[softboy99]

Hi,
In vue2.x, in chapter for "TypeScrpirt Support", there are docuementation about "Class-Style Vue Components"; In vue3, no anything about this. Is it abandoned api? if so, please also give something description. What's the status of https://github.com/vuejs/rfcs/blob/class-api/active-rfcs/0000-class-api.md. Not everyone is clear. Thanks.

[NataliaTepluhina]

@softboy99 Vue Class API proposal has been dropped in favor of the Composition API. If you prefer to use vue-class-component library, please read vuejs/vue-class-component#406

However, this is not a core API and it's still under development so it's not mentioned in the documentation.