[Map] Add missing doc for Circle and Rectangle

Author: Kocal

src/Map/doc/index.rst

@@ -386,6 +386,7 @@ Symfony UX Map allows you to extend its default behavior using a custom Stimulus
             // You can read or write the zoom level
             console.log(event.detail.zoom);
 
+            // You can read or write the center of the map
             console.log(event.detail.center);
 
             // You can read or write map options, specific to the Bridge, it represents the normalized `*Options` PHP class (e.g. `GoogleOptions`, `LeafletOptions`)