update config to use displayData

src/types.ts

@@ -228,7 +228,12 @@ export type CustomElementConfig = {
   type: "custom";
   customType: string;
   transformHandles?: boolean;
-  svg: string | ((element?: ExcalidrawElement) => string | Promise<string>);
+  displayData: {
+    type: "svg" | "dataURL";
+    content:
+      | string
+      | ((element?: ExcalidrawElement) => string | Promise<string>);
+  };
   width?: number;
   height?: number;
   stackedOnTop: boolean;