docs: Update Claude Code instructions in README.md (#711)

Heya, Adam from @anthropics here 👋

We moved our Claude Code MCP docs, this PR updates the link. I've also
added the scope parameter given I think most users will prefer this to
be installed globally (and this matches the installation scope for other
coding assistants).

Author: domdomegg

README.md

@@ -94,7 +94,7 @@ Chrome DevTools MCP will not start the browser instance automatically using this
     Use the Claude Code CLI to add the Chrome DevTools MCP server (<a href="https://code.claude.com/docs/en/mcp">guide</a>):
 
 ```bash
-claude mcp add chrome-devtools npx chrome-devtools-mcp@latest
+claude mcp add chrome-devtools --scope user npx chrome-devtools-mcp@latest
 ```
 
 </details>