docs: document the personalize search parameter

Meilisearch v1.47.0 adds experimental personalized search (a `personalize`
object with a `userContext` string). `Index.search` forwards `opt_params` to the
API as-is, so the parameter already works at runtime; document it alongside the
other common search options.

Closes #1245

Author: tcferreira

meilisearch/index.py

@@ -348,6 +348,8 @@ def search(self, query: str, opt_params: Optional[Mapping[str, Any]] = None) ->
             - hybrid: Dict with 'semanticRatio' and 'embedder' fields for hybrid search
             - vector: Array of numbers for vector search
             - retrieveVectors: Boolean to include vector data in search results
+            - personalize: Dict with a 'userContext' string to personalize the
+              results (experimental; requires Meilisearch >= v1.47)
             - filter: Filter queries by an attribute's value
             - limit: Maximum number of documents returned
             - offset: Number of documents to skip