Ok, actually it didn’t take until the weekend. Working with webassembly still was a pain but it ended up working:
Argon2 using the WASM module in the browser and desktop, and the native bindings in the CLI. Web extensions are yet untested, they will probably not work at all for now.
Still, this needs quite a lot more work to be in a pull-request ready state. Anyways, here is the link: