Link to nested type

[slashmo]

Related to #235, it would be nice if nested types would be linked to:

enum Namespace {
  struct A {}
}

/// - Returns a `Namespace.A`.
func example() -> Namespace.A { Namespace.A() }

Here, the generated HTML currently links the "Namespace" part in the code snippet for the example() method, but not the "A" part.