INTPYTHON-693 Add MongoDBStore to top level README (#173)

Author: blink1073

README.md

@@ -40,6 +40,9 @@ It contains the following packages.
     - [MongoDBSaver](https://langchain-mongodb.readthedocs.io/en/latest/langgraph_checkpoint_mongodb/aio/langgraph.checkpoint.mongodb.aio.AsyncMongoDBSaver.html#asyncmongodbsaver)
     - [AsyncMongoDBSaver](https://langchain-mongodb.readthedocs.io/en/latest/langgraph_checkpoint_mongodb/saver/langgraph.checkpoint.mongodb.saver.MongoDBSaver.html#mongodbsaver)
 
+- Long-term memory (BaseStore)
+   - [MongoDBStore](https://langchain-mongodb.readthedocs.io/en/latest/langgraph_store_mongodb/base/langgraph.store.mongodb.base.MongoDBStore.html#langgraph.store.mongodb.base.MongoDBStore)
+
 ## Installation
 
 You can install the `langchain-mongodb` package from PyPI.