Add CSV customization when adding documents (like delimiter)

[curquiza]

Following meilisearch/meilisearch#2806

Meilisearch accepts CSV dataset, but in a specific format. The users seem to need to customize the format rules of the CSV, like the delimiter

A first solution has been suggested in this PR: meilisearch/meilisearch#2803

[MixusMinimax]

At that point it might even be better to parse the entire csv::readerbuilder from query arguments using serde for example, and this could maybe even apply to json, though there isn't much configurability to json (apart from maybe comments), but I do have to say that delimiters are very commonly something different from commas