"related" API documentation is hard to find #1135

For example, this page: https://docs.hhvm.com/hack/reference/interface/HH.EnumClassAttribute/

This both isn't documented well (I guess a separate issue) and also doesn't tell me any related functionality fits in with this.

I would expect at a minimum that this page would link to related pages (e.g. the enum class base page) but also provide some examples (of any kind but especially) using this in concert with other things in the standard library that it fits in with.