Link to examples/container-instances from SpecialDiff haddocks

Author: Frederick Pringle

src/Generics/Diff/Type.hs

@@ -80,6 +80,10 @@ newtype DiffAtField xss = DiffAtField (NS (ConstructorInfo :*: NS DiffError) xss
 such as lists (see 'ListDiffError'), or even user-defined types that internally preserve invariants
 or have unusual 'Eq' instances. In this case we can implement an instance of 'SpecialDiff' for the
 type.
+
+For concrete examples implementing 'SpecialDiff' on types from "containers", see the
+[examples/containers-instances](https://github.com/fpringle/generic-diff/tree/main/examples/containers-instances)
+directory.
 -}
 class (Show (SpecialDiffError a), Eq (SpecialDiffError a)) => SpecialDiff a where
   -- | A custom diff error type for the special case.