WIP: tzf's Rust port.

• Documents: https://docs.rs/tzf-rs
• Original Go repo: https://github.com/ringsaturn/tzf
• Binary timezone data: https://github.com/ringsaturn/tzf-rel
• Geometry: use https://github.com/ringsaturn/geometry-rs which is https://github.com/tidwall/geometry's Rust port.