docs: provider additional server proxy options (#11828)

Co-authored-by: Ben McCann <[email protected]>

docs/config/server-options.md

@@ -83,7 +83,7 @@ Configure custom proxy rules for the dev server. Expects an object of `{ key: op
 
 Note that if you are using non-relative [`base`](/config/shared-options.md#base), you must prefix each key with that `base`.
 
-Uses [`http-proxy`](https://github.com/http-party/node-http-proxy). Full options [here](https://github.com/http-party/node-http-proxy#options).
+Extends [`http-proxy`](https://github.com/http-party/node-http-proxy#options). Additional options are [here](https://github.com/vitejs/vite/blob/main/packages/vite/src/node/server/middlewares/proxy.ts#L13).
 
 In some cases, you might also want to configure the underlying dev server (e.g. to add custom middlewares to the internal [connect](https://github.com/senchalabs/connect) app). In order to do that, you need to write your own [plugin](/guide/using-plugins.html) and use [configureServer](/guide/api-plugin.html#configureserver) function.