agg: margins

[SkypLabs]

Hi,

This issue follows up on asciinema/asciicast2gif#82.

It would be nice to be able to add margins to the generated GIFs. My use case is to improve the rendering of the GitHub repositories' social media previews.

The template that GitHub provides suggests to add 40px margins around the image.

Cheers.

[ku1ik]

Makes sense to have option like this. If we were to add this I believe it should be opt-in, and customizable, e.g. --margin-width 40 or similar.

[SkypLabs]

Makes sense to have option like this. If we were to add this I believe it should be opt-in, and customizable, e.g. --margin-width 40 or similar.

Yes, it's exactly what I had in mind 👍