buttons: Connect PopUp confirmation display for topics via keypress.

On pressing TOGGLE_MUTE_TOPIC, we now ask for confirmation before
performing the action of muting/unmuting topics.

Author: sumanthvrao

zulipterminal/ui_tools/buttons.py

@@ -309,6 +309,11 @@ def mark_unmuted(self) -> None:
             # All messages in this topic are read.
             self.set_button_counts(0)
 
+    def keypress(self, size: urwid_Size, key: str) -> Optional[str]:
+        if is_command_key('TOGGLE_MUTE_TOPIC', key):
+            self.controller.topic_muting_confirmation_popup(self)
+        return super().keypress(size, key)
+
 
 class UnreadPMButton(urwid.Button):
     def __init__(self, user_id: int, email: str) -> None: