Reference for actions that cause Meilisearch to reindex indexes

[guimachiavelli]

Many actions, such as updating index settings and adding new documents, trigger reindexing. These are usually documented with other features, but we should also have a dedicated and comprehensive list for our own reference.

We might want to make that list available for users too, but the first step is to build it internally.

Tasks

• contact engine team to see which operations outside of index settings cause reindexings
  • if there are many operations outside index settings updates, create a reference page with all of them
  • otherwise mention it in settings reference
• possibly update the index best practices page