docs: add steps for local development (#7449)

* docs: add steps for local development #7434

* docs: minor tweaks

---------

Co-authored-by: dwelle <[email protected]>

README.md

@@ -85,7 +85,7 @@ We'll be adding these features as drop-in plugins for the npm package in the fut
 
 ## Quick start
 
-Install the [Excalidraw npm package](https://www.npmjs.com/package/@excalidraw/excalidraw):
+**Note:** following instructions are for installing the Excalidraw [npm package](https://www.npmjs.com/package/@excalidraw/excalidraw) when integrating Excalidraw into your own app. To run the repository locally for development, please refer to our [Development Guide](https://docs.excalidraw.com/docs/introduction/development).
 
 ```
 npm install react react-dom @excalidraw/excalidraw
@@ -97,7 +97,7 @@ or via yarn
 yarn add react react-dom @excalidraw/excalidraw
 ```
 
-Don't forget to check out our [Documentation](https://docs.excalidraw.com)!
+Check out our [documentation](https://docs.excalidraw.com/docs/@excalidraw/excalidraw/installation) for more details!
 
 ## Contributing