feat: support custom elements in @excalidraw/excalidraw (#5164)

* feat: support custom elements in @excalidraw/excalidraw

* revert

* fix css

* fix offsets

* fix overflow of custom elements in example

* fix overflow in comments input

* make sure comment input never overflows the viewport

* remove offsetschange

* expose setActiveTool

* rename to onPointerDown

* update docs

* fix

src/types.ts

@@ -289,6 +289,11 @@ export interface ExcalidrawProps {
       nativeEvent: MouseEvent | React.PointerEvent<HTMLCanvasElement>;
     }>,
   ) => void;
+  onPointerDown?: (
+    activeTool: AppState["activeTool"],
+    pointerDownState: PointerDownState,
+  ) => void;
+  onScrollChange?: (scrollX: number, scrollY: number) => void;
 }
 
 export type SceneData = {
@@ -449,6 +454,7 @@ export type ExcalidrawImperativeAPI = {
   readyPromise: ResolvablePromise<ExcalidrawImperativeAPI>;
   ready: true;
   id: string;
+  setActiveTool: InstanceType<typeof App>["setActiveTool"];
 };
 
 export type DeviceType = {