docs: resolve.alias for SSR externalized deps (#9337)

Author: sapphi-red

config/shared-options.md

@@ -110,6 +110,10 @@ When aliasing to file system paths, always use absolute paths. Relative alias va
 
 More advanced custom resolution can be achieved through [plugins](/guide/api-plugin).
 
+::: warning Using with SSR
+If you have configured aliases for [SSR externalized dependencies](/guide/ssr.md#ssr-externals), you may want to alias the actual `node_modules` packages. Both [Yarn](https://classic.yarnpkg.com/en/docs/cli/add/#toc-yarn-add-alias) and [pnpm](https://pnpm.js.org/en/aliases) support aliasing via the `npm:` prefix.
+:::
+
 ## resolve.dedupe
 
 - **Type:** `string[]`