Include type constraints in documentation

[TysonMN]

The documentation for hash does not say that it requires the equality constraint on its only type parameter. Another example is the documentation for compare. It requires the comparison type constraint on its only type parameter. For convenience, here is the list of all type constraints.

Could type constraints be added to the documentation for types that have them?

(I original created this issue at https://github.com/fsharp/fsharp-core-docs/issues/65 instead of here.)