Update settings before adding documents

[dichotommy]

Updating the settings causes all documents to be reindexed. This is normal for a search engine database.

This means that the best practice for starting a new MeiliSearch index is to update the index settings first, then add documents. This halves RAM consumption, since you only index the documents once (on add), vs. if you add documents then update settings you are actually indexing your documents twice (1. on add 2. on settings update).

This info should be added to the docs.