views: Indicate configuring/enabling notifications if checkbox disabled.

This commit adds an extra Text widget in the stream settings indicating the
user to configure or enable notifications if the checkbox is disabled.

Currently, there are two ways to enable notifications in ZT:
- Pass the --notify flag when starting ZT.
- Add notify=enabled in the zuliprc file.

Author: zee-bit

zulipterminal/ui_tools/views.py

@@ -1330,6 +1330,12 @@ def __init__(self, controller: Any, stream_id: int) -> None:
         self.widgets.append(muted_setting)
         self.widgets.append(pinned_setting)
         self.widgets.append(visual_notification)
+        if not self.controller.notify_enabled:
+            self.widgets.append(
+                urwid.Text(
+                    ("msg_bold", "    [notifications not configured or enabled]")
+                )
+            )
         super().__init__(controller, self.widgets, "STREAM_DESC", popup_width, title)
 
     def toggle_mute_status(self, button: Any, new_state: bool) -> None: