Add preview links for new methods

Author: Stephen Barlow

docs/source/index.mdx

@@ -9,7 +9,12 @@ import { colors } from 'gatsby-theme-apollo-core';
 
 > Apollo Client 3.5 is available as a release candidate ([learn about release stages](https://www.apollographql.com/docs/resources/release-stages/#open-source-release-stages)).
 >
-> For a summary of updates, see the [changelog](https://github.com/apollographql/apollo-client/blob/release-3.5/CHANGELOG.md).
+> **See the preview documentation for:**
+>
+> * Cache methods [`updateQuery` and `updateFragment`](https://deploy-preview-8554--apollo-client-docs.netlify.app/caching/cache-interaction/#using-updatequery-and-updatefragment)
+> * `useMutation` helper function [`reset`](https://deploy-preview-8554--apollo-client-docs.netlify.app/data/mutations/#resetting-mutation-status)
+>
+> For all updates, see the [changelog](https://github.com/apollographql/apollo-client/blob/release-3.5/CHANGELOG.md).
 
 **Apollo Client** is a comprehensive state management library for JavaScript that enables you to manage both local and remote data with GraphQL. Use it to fetch, cache, and modify application data, all while automatically updating your UI.