Graph doesn't include ancestors of post-process @imported files

[flovan]

I know you aren't technically maintaining this repo anymore (though you did merge a PR recently) in favour of https://github.com/lox/sass-graph, but I have stumbled onto a problem that I'd like to find a solution for.

If I run this module, it parses the file directories once and then works from the generated graph. But if I @import a file after the process has started, the graph doesn't find an ancestor for it, so no file will get pushed through in the end.

If you don't plan on fixing this, would you be willing to accept a PR for this (if I find a solution at all)?