docs: guide of extending vite config (#1874)

Co-authored-by: Ctibor Laky <laky@efabrica.sk>
Co-authored-by: Anthony Fu <anthonyfu117@hotmail.com>

docs/config/index.md

@@ -51,6 +51,20 @@ export default defineConfig({
 })
 ```
 
+When using a separate `vitest.config.js`, you can also extend Vite's options from another config file if needed:
+
+```ts
+import { mergeConfig } from 'vite'
+import { defineConfig } from 'vitest/config'
+import viteConfig from './vite.config'
+
+export default mergeConfig(viteConfig, defineConfig({
+ test: {
+ exclude: ['packages/template/*'],
+ },
+}))
+```
+
 ## Options
 
 :::tip