Added notes on attributesToIndex
Added notes on attributesToIndex

rastech/algoliasearch-client-go,algoliareadmebot/algoliasearch-client-go,l4u/algoliasearch-client-go,bountylabs/algoliasearch-client-go,l4u/algoliasearch-client-go,algolia/algoliasearch-client-go,algolia/algoliasearch-client-go