woltapp/wolt_modal_sheet ? reverse-engineered prompt

Build me a Flutter package for a polished modal sheet that works well on phones and larger screens.

I want it to support multiple pages inside one modal, smooth animated transitions when moving between pages, and scrollable content on each page without feeling cramped. It should feel flexible enough to use as a bottom sheet, side sheet, dialog, or alert style modal depending on screen size, and it should be easy to customize the look and behavior for different apps.

Please include a simple starter example so I can open it and immediately see how to show the modal, add a few pages, and move between them. Also make sure the code is clean, documented, and usable from both simple and more advanced Flutter apps. If you need to check current Flutter docs or best practices online, go ahead and do that.