docs[patch]: Adds diagram to installation guide

docs/core_docs/docs/how_to/installation.mdx

@@ -20,7 +20,7 @@ However, note that individual integrations may not be supported in all environme
 
 ## Installation
 
-To install LangChain, run the following command:
+To install the main `langchain` package, run:
 
 import Tabs from "@theme/Tabs";
 import TabItem from "@theme/TabItem";
@@ -30,8 +30,25 @@ import CodeBlock from "@theme/CodeBlock";
 npm install langchain
 ```
 
-A lot of the value of LangChain comes when integrating it with various model providers, datastores, etc.
+While this package acts as a sane starting point to using LangChain,
+much of the value of LangChain comes when integrating it with various model providers, datastores, etc.
 By default, the dependencies needed to do that are NOT installed. You will need to install the dependencies for specific integrations separately.
+We'll show how to do that in the next sections of this guide.
+
+Please also see the section on [installing integration packages](/docs/how_to/installation/#installing-integration-packages)
+for some special considerations.
+
+## Ecosystem packages
+
+With the exception of the `langsmith` SDK, all packages in the LangChain ecosystem depend on `@langchain/core`, which contains base
+classes and abstractions that other packages use. The dependency graph below shows how the difference packages are related.
+A directed arrow indicates that the source package depends on the target package:
+
+![](/img/ecosystem_packages.png)
+
+When installing a package, you do not need to explicitly install that package's explicit dependencies (such as `@langchain/core`).
+However, you may choose to if you are using a feature only available in a certain version of that dependency.
+If you do, you should make sure that the installed or pinned version is compatible with any other integration packages you use.
 
 ### @langchain/community
 
@@ -55,7 +72,7 @@ npm install @langchain/core
 
 ### LangGraph
 
-`langgraph` is a library for building stateful, multi-actor applications with LLMs, built on top of (and intended to be used with) LangChain.
+[LangGraph.js](https://langchain-ai.github.io/langgraphjs/) is a library for building stateful, multi-actor applications with LLMs.
 Install with:
 
 ```bash npm2yarn