Layout margin: default and configuration

[not-my-profile]

The padding of the diagram is currently hard coded to 80px:

oxdraw/src/lib.rs

Line 22 in bb53da9

pub const LAYOUT_MARGIN: f32 = 80.0;

Personally I think this is way too much. When viewing such an image on mobile with a max-width: 100% it leads to wasted space.
mermaid-js apparently defaults to 8px, graphviz to 8 points (whatever a point is but it looks similar).

So I think it would be nice if the default would be lowered and perhaps in addition made configurable with yet another CLI option (though #45 would help with that).

[RohanAdwankar]

Thanks for the Issue! I think a cli flag would definitely be a good idea. I'll try out some margin values and see what seems reasonable for a default but I appreciate letting me know about what mermaid and graphviz use if lower margins are generally preferred I'll probably lower them as well.

[not-my-profile]

You're welcome! The thing is that more margins can generally be easily added in whatever layout system you're using e.g. in CSS whereas removing margins isn't that easy and introduces a dependency on the margins used to create the files, if that makes sense? And doing the margins in CSS is more flexible anyway since you can also take the viewport into account.