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/announcements.py

@@ -0,0 +1,36 @@
+# -*- coding: utf-8 -*-
+import wx
+from multiplatform_widgets import widgets
+
+class announcementsPanel(wx.Panel):
+
+    def set_focus_function(self, f):
+        self.list.list.Bind(wx.EVT_LIST_ITEM_FOCUSED, f)
+
+    def create_list(self):
+        self.list = widgets.list(self, _("Announcement"), style=wx.LC_REPORT|wx.LC_SINGLE_SEL|wx.LC_VRULES)
+        self.list.set_windows_size(0, 800)
+        self.list.set_size()
+
+    def __init__(self, parent, name):
+        super(announcementsPanel, self).__init__(parent)
+        self.name = name
+        self.type = "baseBuffer"
+        self.sizer = wx.BoxSizer(wx.VERTICAL)
+        self.create_list()
+        self.dismiss = wx.Button(self, -1, _("Dismiss"))
+        btnSizer = wx.BoxSizer(wx.HORIZONTAL)
+        btnSizer.Add(self.dismiss, 0, wx.ALL, 5)
+        self.sizer.Add(btnSizer, 0, wx.ALL, 5)
+        self.sizer.Add(self.list.list, 1, wx.ALL|wx.EXPAND, 5)
+        self.SetSizer(self.sizer)
+        self.SetClientSize(self.sizer.CalcMin())
+
+    def set_position(self, reversed=False):
+        if reversed == False:
+            self.list.select_item(self.list.get_count()-1)
+        else:
+            self.list.select_item(0)
+
+    def set_focus_in_list(self):
+        self.list.list.SetFocus()