[simple] add ddg-search to __init__ for easier loading (#3933)

the same as other tools

langchain/utilities/__init__.py

@@ -5,6 +5,7 @@ from langchain.utilities.arxiv import ArxivAPIWrapper
 from langchain.utilities.awslambda import LambdaWrapper
 from langchain.utilities.bash import BashProcess
 from langchain.utilities.bing_search import BingSearchAPIWrapper
+from langchain.utilities.duckduckgo_search import DuckDuckGoSearchAPIWrapper
 from langchain.utilities.google_places_api import GooglePlacesAPIWrapper
 from langchain.utilities.google_search import GoogleSearchAPIWrapper
 from langchain.utilities.google_serper import GoogleSerperAPIWrapper
@@ -21,6 +22,7 @@ __all__ = [
     "ArxivAPIWrapper",
     "BashProcess",
     "TextRequestsWrapper",
+    "DuckDuckGoSearchAPIWrapper",
     "GoogleSearchAPIWrapper",
     "GoogleSerperAPIWrapper",
     "GooglePlacesAPIWrapper",