Add Tutorial on Using the Ruby SDK's CouchbaseStore in Rails ActiveSupport

The Ruby SDK offers a cache implementation for Rails built in: https://docs.couchbase.com/sdk-api/couchbase-ruby-client/ActiveSupport/Cache/CouchbaseStore.html. However, there is minimal documentation explaining how to use it, except for the API reference. As this is a notable feature and one that would be highly beneficial to Rails devs building with Couchbase, it could be a good idea to create a quickstart guide, tutorial or similar in the documentation explaining how to use this functionality.