Fix facetFilters type

[aseure]

The facetFilters parameter is currently typed as a Seq[String]. However, it can either be used as:

• String
• Seq[String]
• Seq[Seq[String]]
• Seq[?] where ? can be a composed of both Seq[String] or String

See our documentation for more details: https://www.algolia.com/doc/api-reference/api-parameters/facetFilters/.

Quick fix may be to introduce a new FacetFilters type to represent all those options but it's a breaking change and it would have to wait for another major release. We can also introduce a new field with this type and deprecate the original facetFilters fields but it would be misleading for the user not to use the actual Algolia parameter name.