TouchMenu: Search menu to search the menu (#9876)

Fixes #9800.

frontend/apps/reader/readerui.lua

@@ -871,4 +871,11 @@ function ReaderUI:getCurrentPage()
     end
 end
 
+function ReaderUI:onMenuSearch()
+    if not self.ui then
+        self.menu:onShowMenu()
+    end
+    self.menu.menu_container[1]:onShowMenuSearch()
+end
+
 return ReaderUI