[doc] Add TOC to offline mode guide
[doc] Add TOC to offline mode guide

[ci skip]
algoliareadmebot/algoliasearch-client-swift,algolia/algoliasearch-client-swift,algolia/algoliasearch-client-swift,algoliareadmebot/algoliasearch-client-swift,algoliareadmebot/algoliasearch-client-swift