doc: add example for running with v8-inspector

Add example to show what running Node.js with `--inspect`
should look like.

Some IDEs do not show the link when running with `--inspect`.
This example hints to what the full output looks like.

PR-URL: #8845
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Myles Borins <myles.borins@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>

doc/api/debugger.md

@@ -193,4 +193,12 @@ e.g. `--inspect=9222` will accept DevTools connections on port 9222.
 To break on the first line of the application code, provide the `--debug-brk`
 flag in addition to `--inspect`.
 
+```txt
+$ node --inspect index.js
+Debugger listening on port 9229.
+Warning: This is an experimental feature and could change at any time.
+To start debugging, open the following URL in Chrome:
+    chrome-devtools://devtools/remote/serve_file/@60cd6e859b9f557d2312f5bf532f6aec5f284980/inspector.html?experiments=true&v8only=true&ws=localhost:9229/node
+```
+
 [TCP-based protocol]: https://github.com/v8/v8/wiki/Debugging-Protocol