thank you for the addon my eyes can now rest

Thank you for this helpful extension!
With more and more phone manufacturers following the rather stupid trend of using displays with rounded sides that distort the content in the left and right corners of the screen, this extension is great at keeping websites away from those corners.

I'd like to make two suggestions for improvement in this context:
- Give users the option to set a default margin size.
- Larger buttons for the mobile version of Firefox, if possible. Right now the way it works on mobile devices is that you get a new tab with tiny buttons that you have to zoom into first.