[Feature Request] Weighted distances

Hi there!

Coming from using the [RapidFuzz](https://github.com/maxbachmann/RapidFuzz) library in Python, a feature I liked to use was weighted distances. [RapidFuzz Docs](https://maxbachmann.github.io/RapidFuzz/Usage/distance/Levenshtein.html#distance).

Do you think this would be possible to implement here without too much issue? I know parameters might pose a design problem as there are no optional arguments in Rust and having every function always take weights might be annoying to users. Maybe a separate function would be useful? Would you be open to contributions?

Thanks in advance for responding!