docs: add temp_dataset_name to community.BigQueryVectorStore docs (#735)

libs/community/langchain_google_community/bq_storage_vectorstores/bigquery.py

@@ -36,6 +36,9 @@ class BigQueryVectorStore(BaseBigQueryVectorStore):
     `batch_search` method.
     Optionally, this class can leverage a Vertex AI Feature Store for online serving
     through the `to_vertex_fs_vector_store` method.
+    Note that the `bigquery.datasets.create permission` is required even if the
+    dataset already exists. This can be avoided by specifying `temp_dataset_name` as
+    the name of an existing dataset.
 
     Attributes:
         embedding: Embedding model for generating and comparing embeddings.
@@ -46,6 +49,8 @@ class BigQueryVectorStore(BaseBigQueryVectorStore):
         content_field: Name of the column storing document content (default: "content").
         embedding_field: Name of the column storing text embeddings (default:
             "embedding").
+        temp_dataset_name: Name of the BigQuery dataset to be used to upload temporary
+            BQ tables. If None, will default to "{dataset_name}_temp".
         doc_id_field: Name of the column storing document IDs (default: "doc_id").
         credentials: Optional Google Cloud credentials object.
         embedding_dimension: Dimension of the embedding vectors (inferred if not