Add section to Download page for IntelliSense extension (#41492)

Author: mdo

site/src/content/docs/getting-started/download.mdx

@@ -150,3 +150,11 @@ Install-Package bootstrap
 ```powershell
 Install-Package bootstrap.sass
 ```
+
+## IntelliSense extension
+
+<img class="d-block mb-4 img-fluid rounded-3" src="/docs/[[config:docs_version]]/assets/img/bootstrap-intellisense-autocomplete.png" width="573" height="332" alt="" />
+
+Install the community-maintained [IntelliSense extension](https://marketplace.visualstudio.com/items?itemName=hossaini.bootstrap-intellisense) for Visual Studio Code to get IntelliSense auto-completion for Bootstrap classes.
+
+<a href="https://marketplace.visualstudio.com/items?itemName=hossaini.bootstrap-intellisense" class="btn btn-bd-primary">View in VS Code Marketplace</a>