feat: add global channel search support (#3694)

Co-authored-by: Rasmus Karlsson <rasmus.karlsson@pajlada.com>

src/widgets/splits/Split.hpp

@@ -171,7 +171,7 @@ public slots:
     void copyToClipboard();
     void startWatching();
     void setFiltersDialog();
-    void showSearch();
+    void showSearch(bool singleChannel);
     void showViewerList();
     void openSubPage();
     void reloadChannelAndSubscriberEmotes();