Lots of pages have no docs at all

[bigfootjon]

A few examples just from clicking around randomly:

• https://docs.hhvm.com/hack/reference/interface/HH.TypeConstantAttribute/
• https://docs.hhvm.com/hack/reference/interface/HH.StaticPropertyAttribute/
• https://docs.hhvm.com/hack/reference/interface/HH.Lib.SQL.QueryFormat/
• https://docs.hhvm.com/hack/reference/interface/HH.EnumAttribute/

As a Meta engineer, I can just grep for examples and reverse-engineer how something should be used, but having docs (even for rarely used things) would increase my ability to rely on these docs instead of just searching around for someone already using it and cargo-culting implementation details.