docs(composables): add nested and plugin injection examples

docs/content/2.guide/3.directory-structure/5.composables.md

@@ -12,7 +12,7 @@ Under the hood, Nuxt auto generates the file `.nuxt/auto-imports.d.ts` to declar
 
 Be aware that you have to run `nuxi prepare`, `nuxi dev` or `nuxi build` in order to let Nuxt generates the types. If you create a composable without having the dev server running, typescript will throw an error `Cannot find name 'useBar'.`
 
-## Example
+## Usage
 
 **Method 1:** Using named export
 
@@ -47,6 +47,30 @@ const foo = useFoo()
 
 :LinkExample{link="/examples/auto-imports/composables"}
 
+## Examples
+
+### Nested Composables
+
+You can use a composable within another composable using auto imports:
+
+```js [composables/test.ts]
+export const useFoo = () => {
+  const nuxtApp = useNuxtApp()
+  const bar = useBar()
+}
+```
+
+### Access plugin injections
+
+You can access [plugin injections](/guide/directory-structure/plugins#automatically-providing-helpers) from composables:
+
+```js [composables/test.ts]
+export const useHello = () => {
+  const nuxtApp = useNuxtApp()
+  return nuxtApp.$hello
+}
+```
+
 ## How Files Are Scanned
 
 Nuxt only scans files at the top level of the `composables/` directory, e.g.: