docs(vscode): add Marketplace install instructions and badge

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ryanbas21

packages/vscode-extension/README.md

@@ -1,7 +1,21 @@
 # OIDC DevTools — VS Code Extension
 
+[![VS Code Marketplace](https://img.shields.io/visual-studio-marketplace/v/RyanBasmajian.oidc-devtools)](https://marketplace.visualstudio.com/items?itemName=RyanBasmajian.oidc-devtools)
+
 VS Code extension for live OIDC/OAuth2 debugging. Connects to Chrome/Chromium via the Chrome DevTools Protocol (CDP) to capture and analyze authentication flows without leaving your editor.
 
+## Install
+
+**From the Marketplace:** [OIDC DevTools](https://marketplace.visualstudio.com/items?itemName=RyanBasmajian.oidc-devtools)
+
+**From the command line:**
+
+```bash
+code --install-extension RyanBasmajian.oidc-devtools
+```
+
+**From VS Code:** Open Extensions (`Ctrl+Shift+X`), search for "OIDC DevTools", and click Install.
+
 ## Features
 
 - **Live network capture** — captures auth-related traffic via CDP (`Network` domain)