feat(docs): add PGVectorStore (#30950)

Thank you for contributing to LangChain!

-  **Adding documentation for PGVectorStore**: 
docs: Adding documentation for the new PGVectorStore as a part of
langchain-postgres

- **Add docs**: The notebook for PGVectorStore is now added to the
directory `docs/docs/integrations`.
As a part of this change, we've also updated the VectorStore features
table and VectorStoreTabs

---------

Co-authored-by: Chester Curme <chester.curme@gmail.com>
Co-authored-by: Eugene Yurtsev <eyurtsev@gmail.com>

docs/scripts/vectorstore_feat_table.py

@@ -10,6 +10,7 @@ from langchain_couchbase import CouchbaseSearchVectorStore
 from langchain_milvus import Milvus
 from langchain_mongodb import MongoDBAtlasVectorSearch
 from langchain_pinecone import PineconeVectorStore
+from langchain_postgres import PGVectorStore
 from langchain_qdrant import QdrantVectorStore
 
 vectorstore_list = [
@@ -22,6 +23,7 @@ vectorstore_list = [
 ]
 
 from_partners = [
+    ("PGVectorStore", PGVectorStore),
     ("Chroma", Chroma),
     ("AstraDBVectorStore", AstraDBVectorStore),
     ("QdrantVectorStore", QdrantVectorStore),
@@ -52,6 +54,17 @@ The table below lists the features for some of our most popular vector stores.
 
 def get_vectorstore_table():
     vectorstore_feat_table = {
+        "PGVectorStore": {
+            "Delete by ID": True,
+            "Filtering": True,
+            "similarity_search_by_vector": True,
+            "similarity_search_with_score": True,
+            "asearch": True,
+            "Passes Standard Tests": True,
+            "Multi Tenancy": False,
+            "Local/Cloud": "Local",
+            "IDs in add Documents": True,
+        },
         "FAISS": {
             "Delete by ID": True,
             "Filtering": True,