generate a directory tree of md links
cargo run -- <target-dir (defaults to .)>.
├───Cargo.lock
├───Cargo.toml
├───src
│ ├───generate_tree.rs
│ ├───main.rs
│ ├───markdown.rs
│ ├───print_tree.rs
│ └───write_tree.rs
├───test.md
└───tree.md\
[] spaces getting collapsed [] last entry shows backslash