f94753c511
Previously, `filter_fn` on the `WalkOptions` struct looked like:
pub filter_fn: Option<Box<&'static FilterFn>>,
This boxing was unneccesary and has been changed to:
pub filter_fn: Option<&'static FilterFn>,
This will only affect people who use obsidian-export as a library in
other Rust programs, not users of the CLI.
For those library users, they no longer need to supply `FilterFn`
wrapped in a Box.