v 6.8.3

• In-app markdown file viewer.
• Native Instant View support.
• Native external webapp viewer on Linux.
• Screen reader support for chat list and message list.
• Fix Ctrl+Shift+V on non-English layouts.
• Upgrade to Qt 6.11.1 on macOS and Linux.
• Test QRhi for Thanos effect on Qt 6.11.1.