Breaks for browsers with scrollbars

[pichfl]

Makes the demo a bit less minimal than intended.

Happens on macOS 10.13.5 using Safari 11.1.1.

[RobbieTheWagner]

Hi @pichfl thanks for reporting! Which browser is that? Would you be interested in submitting a PR to help resolve this?

[pichfl]

Sorry for missing the details, I've updated the message above. No, we don't have a project that will use this addon as of now, but I thought I'd pass it along.