docs: update maintenance badge to 2026

Author: josdejong

README.md

@@ -2,7 +2,7 @@
 
 [![Version](https://img.shields.io/npm/v/jsoneditor.svg)](https://www.npmjs.com/package/jsoneditor)
 [![Downloads](https://img.shields.io/npm/dm/jsoneditor.svg)](https://www.npmjs.com/package/jsoneditor)
-[![Maintenance](https://img.shields.io/maintenance/yes/2025.svg)](https://github.com/josdejong/jsoneditor/pulse)
+[![Maintenance](https://img.shields.io/maintenance/yes/2026.svg)](https://github.com/josdejong/jsoneditor/pulse)
 [![License](https://img.shields.io/github/license/josdejong/jsoneditor.svg)](https://github.com/josdejong/jsoneditor/blob/master/LICENSE)
 [![FOSSA Status](https://app.fossa.io/api/projects/git%2Bgithub.com%2Fjosdejong%2Fjsoneditor.svg?type=shield)](https://app.fossa.io/projects/git%2Bgithub.com%2Fjosdejong%2Fjsoneditor?ref=badge_shield)