feat(docs): describe buildNuxt utility

docs/3.api/4.advanced/2.kit.md

@@ -139,7 +139,25 @@ Loading conditions for Nuxt. `loadNuxt` uses [`c12`](https://github.com/unjs/c12
 
   Overrides for the Nuxt configuration.
 
-### `buildNuxt(nuxt)`
+### `buildNuxt`
+
+Build Nuxt programmatically. It will invoke the builder (curently [@nuxt/vite-builder](https://github.com/nuxt/nuxt/tree/main/packages/vite) or [@nuxt/webpack-builder](https://github.com/nuxt/nuxt/tree/main/packages/webpack)) to bundle the application.
+
+#### Type
+
+```ts
+async function buildNuxt (nuxt: Nuxt): Promise<any>
+```
+
+#### Parameters
+
+##### `nuxt`
+
+**Type**: `Nuxt`
+
+**Required**: `true`
+
+Nuxt instance to build. It can be retrieved from the context via `useNuxt()` call.
 
 ### `loadNuxtConfig(loadOptions)`