Stacked Errors

This is a very WIP experimental errors crate with the purpose to provide better error debuggability in async call stacks (backtraces are basically useless in async tasks). What we do is take advantage of #[track_caller] and create two stacks of Locations and errors via the helpful MapAddErr trait.

Please file a PR if there is some error type you would like to support directly in the enum or add some other improvement.