feat(mastodon): Add support for server announcements

Implemented a new 'Announcements' buffer to view instance-wide news. Features include:

- New buffer and UI panel for announcements.

- Support for templates and rendering of announcement content.

- 'Dismiss' functionality (mapped to Enter/Return) to mark announcements as read.

- Integrated into account settings for buffer management.

src/wxUI/buffers/mastodon/__init__.py

@@ -2,4 +2,5 @@
 from .base import basePanel
 from .conversationList import conversationListPanel
 from .notifications import notificationsPanel
-from .user import userPanel
+from .user import userPanel
+from .announcements import announcementsPanel