feat: re-export rayon in the crate root.

This makes creating a `ThreadPool` easier as it doesn't force us to
maintain our own `rayon` dependency.

src/lib.rs

@@ -126,6 +126,7 @@ use std::sync::Arc;
 use crate::core::{ReadDir, ReadDirSpec};
 
 pub use crate::core::{DirEntry, DirEntryIter, Error};
+pub use rayon;
 
 /// Builder for walking a directory.
 pub type WalkDir = WalkDirGeneric<((), ())>;