Add a badge to the bell icon on new notifications (#6751)

It changes the icon if a new notification event is consumed and changes
it back to normal upon toggling NotificationPanel.

Added a new field to NotificationPanel:
	- have_unseen_notifications: bool

Added a new icon asset
	- IconName::BellBadged => "assets/icons/bell_badged.svg"

Release Notes:

- Added a badge to bell icon for new notifications
([#6721](https://github.com/zed-industries/zed/issues/6721)).

crates/ui/src/components/icon.rs

@@ -39,6 +39,7 @@ pub enum IconName {
     Bell,
     BellOff,
     BellRing,
+    BellBadged,
     Bolt,
     CaseSensitive,
     Check,
@@ -130,6 +131,7 @@ impl IconName {
             IconName::Bell => "icons/bell.svg",
             IconName::BellOff => "icons/bell_off.svg",
             IconName::BellRing => "icons/bell_ring.svg",
+            IconName::BellBadged => "icons/bell_badged.svg",
             IconName::Bolt => "icons/bolt.svg",
             IconName::CaseSensitive => "icons/case_insensitive.svg",
             IconName::Check => "icons/check.svg",