Add Scrollbars when using JS Paint on Firefox for Android

Most Websites are made to function well without tangible Scrollbars on Touchscreens. That is not the Case for JS Paint.

The Lack of Scrollbars sometimes makes it difficult to tell where i am, relative to the Canvas Size. And the two‑Finger‑Pinch to scroll doesn’t really work: I can scroll vertically but not horizontally.

In Conclusion, JS Paint on Touchscreens really needs oldschool Scrollbars.