chore: update to ESLint v9

Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>

Author: susnux

.eslintignore

@@ -0,0 +1,11 @@
+/*!
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: CC0-1.0
+ */
+
+import { recommendedLibrary } from '@nextcloud/eslint-config'
+import { defineConfig } from 'eslint/config'
+
+export default defineConfig([
+	...recommendedLibrary,
+])