docs ecosystem/integrations update 4 (#5590)

# docs `ecosystem/integrations` update 4

Added missed integrations. Fixed inconsistencies. 

## Who can review?

@hwchase17 
@dev2049

docs/integrations/chroma.md

@@ -1,20 +1,29 @@
 # Chroma
 
-This page covers how to use the Chroma ecosystem within LangChain.
-It is broken into two parts: installation and setup, and then references to specific Chroma wrappers.
+>[Chroma](https://docs.trychroma.com/getting-started) is a database for building AI applications with embeddings.
 
 ## Installation and Setup
-- Install the Python package with `pip install chromadb`
-## Wrappers
 
-### VectorStore
+```bash
+pip install chromadb
+```
+
+
+## VectorStore
 
 There exists a wrapper around Chroma vector databases, allowing you to use it as a vectorstore,
 whether for semantic search or example selection.
 
-To import this vectorstore:
 ```python
 from langchain.vectorstores import Chroma
 ```
 
 For a more detailed walkthrough of the Chroma wrapper, see [this notebook](../modules/indexes/vectorstores/getting_started.ipynb)
+
+## Retriever
+
+See a [usage example](../modules/indexes/retrievers/examples/chroma_self_query.ipynb).
+
+```python
+from langchain.retrievers import SelfQueryRetriever
+```