It should probably additionally throw on empty string? But maybe someone has a use case there...

Additionally:

• enforce no duplicate whitespace
• enforce non-zero length
• enforce only printable characters

Akin to whirlpool-client-cli's deposit's increment=true argument documented here, allow a user to generate an address and mark it as used (or simply allow a user to mark an already generated address as used).

This would allow us

AFAIK only English and Japanese exist, so that leaves only Japanese todo. But it would be great if we get get or create vectors for each language we support. Anybody speak Spanish, Italian, Chinese, or Korean?

I noticed that when you click in the documentation you get taken to the instructions for version 0.5.1, which has examples that aren't in compliance with the most up to date version of this crate.
Since the actual link being used is https://docs.rs/bip39, I think this problem is with docs.rs, and nothing in the actual repository.