feat(docs): describe loadNuxtConfig utility

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

@@ -159,7 +159,25 @@ async function buildNuxt (nuxt: Nuxt): Promise<any>
 
 Nuxt instance to build. It can be retrieved from the context via `useNuxt()` call.
 
-### `loadNuxtConfig(loadOptions)`
+### `loadNuxtConfig`
+
+Load Nuxt configuration. It will return the promise with the configuration object.
+
+#### Type
+
+```ts
+async function loadNuxtConfig (opts: LoadNuxtConfigOptions): Promise<NuxtOptions>
+```
+
+#### Parameters
+
+##### `opts`
+
+**Type**: `LoadNuxtConfigOptions`
+
+**Required**: `true`
+
+Options to pass in [`c12`](https://github.com/unjs/c12#options) `loadConfig` call.
 
 ## Compatibility