Add aria-expanded to settings accordion button

Mark settings button that triggers the expand/collaps of the
side nav settings with aria-expanded attribute to improve accesibility.

Resolves : nextcloud/server#37136

Signed-off-by: fenn-cs <fenn25.fn@gmail.com>

src/components/NcAppNavigationSettings/NcAppNavigationSettings.vue

@@ -27,6 +27,9 @@
 		<div id="app-settings__header">
 			<button class="settings-button"
 				type="button"
+				:aria-expanded="open"
+				aria-controls="app-settings__content"
+				aria-label="t('Open settings menu')"
 				@click="toggleMenu">
 				<Cog class="settings-button__icon" :size="20" />
 				<span class="settings-button__label">{{ title }}</span>