Add link to fragment matcher recipe (apollographql#3284)

packages/apollo-cache-inmemory/README.md

@@ -34,10 +34,7 @@ The `InMemoryCache` constructor takes an optional config object with properties
 
 - addTypename: A boolean to determine whether to add __typename to the document (default: `true`)
 - dataIdFromObject: A function that takes a data object and returns a unique identifier to be used when normalizing the data in the store. Learn more about how to customize `dataIdFromObject` in the [Normalization](#normalization) section.
-- fragmentMatcher: By default, the `InMemoryCache` uses a heuristic fragment matcher. If you are using fragments on unions and interfaces, you will need to use an `IntrospectionFragmentMatcher`. For more information, please read [our guide to setting up fragment matching for unions & interfaces].
-<!---
-TODO (PEGGY): Add link to fragment matcher recipe
--->
+- fragmentMatcher: By default, the `InMemoryCache` uses a heuristic fragment matcher. If you are using fragments on unions and interfaces, you will need to use an `IntrospectionFragmentMatcher`. For more information, please read [our guide to setting up fragment matching for unions & interfaces](https://www.apollographql.com/docs/react/advanced/fragments.html#fragment-matcher).
 
 <h2 id="normalization">Normalization</h2>