fix(notifications): We advertise notification markup support, enable it

I previously had this disabled to workaround Thunderbird in particular,
but many other applications correctly support markup, so we should
either disable advertising it, or correctly enable it. Opted for the
latter.

cmd/hyprpanel-client/notification_item.go

@@ -149,9 +149,9 @@ func (i *notificationItem) build(container *gtk.Box) error {
 	body := gtk.NewLabel(``)
 	i.AddRef(body.Unref)
 	body.SetSelectable(true)
-	// I'd love to be able to use SetMarkup here, but Thunderbird for example does not
-	// entity encode <> which results in empty notifications.
-	body.SetText(i.data.Body)
+	// Enable markup output, but beware that Thunderbird does not correclty encode their messages:
+	// https://bugzilla.mozilla.org/show_bug.cgi?id=1432209
+	body.SetMarkup(i.data.Body)
 	body.SetVexpand(true)
 	body.SetWrap(true)
 	body.SetWrapMode(pango.WrapWordCharValue)