Validate fragment name uniqueness

src/Language/GraphQL/Validate/Validation.hs

@@ -48,6 +48,7 @@ data Validation m = Validation
 data Rule m
     = DefinitionRule (Definition -> RuleT m)
     | OperationDefinitionRule (OperationDefinition -> RuleT m)
+    | FragmentDefinitionRule (FragmentDefinition -> RuleT m)
 
 -- | Monad transformer used by the rules.
 type RuleT m = ReaderT (Validation m) Maybe Error