feat: Add support for scrollToCenter in initialData so host can control whether to scroll to center on mount (#3070)

* feat: Add support for scrollToCenter in initialData so host can control whether to scroll to center on mount

* fix

* update changelog and readme

* fix

* Scroll to center only for collab and shareable links in excalidraw app

* fix test

* update readme

* Update src/packages/excalidraw/README.md

src/tests/scroll.test.tsx

@@ -30,6 +30,7 @@ describe("appState", () => {
               height: ELEM_HEIGHT,
             }),
           ],
+          scrollToCenter: true,
         }}
       />,
     );