chore(docs): add documentation section for composables

Signed-off-by: Maksim Sukharev <[email protected]>

docs/composables.md

@@ -0,0 +1,27 @@
+<!--
+ - SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
+ - SPDX-License-Identifier: AGPL-3.0-or-later
+-->
+
+### Registration
+
+To use any composable, import and use it according to documentation or Vue guidelines, for example:
+
+```js static
+import { useIsMobile } from '@nextcloud/vue/dist/composables/useIsMobile.js'
+
+export default {
+	setup() {
+		return {
+			isMobile: useIsMobile(),
+		}
+	},
+}
+```
+or in `<script setup>`:
+
+```js static
+import { useIsMobile } from '@nextcloud/vue/dist/composables/useIsMobile.js'
+
+const isMobile = useIsMobile()
+```

styleguide.config.js

@@ -139,6 +139,13 @@ module.exports = async () => {
 					},
 				],
 			},
+			{
+				name: 'Composables',
+				content: 'docs/composables.md',
+				sectionDepth: 1,
+				sections: [
+				],
+			},
 			{
 				name: 'Components',
 				content: 'docs/components.md',