How to sign a document in browser with jks file?

Question

JavaScript

Good afternoon.
Actually it is necessary to sign the data sent by the browser.
Forge seems to work with PKCS12 .
For "unique" Ukrainian format - jkurwa .
But Privat24 issues keys in the jks repository. And the format seems to be popular. But I could not find a javascript library that would work with it on the client side?
Maybe someone can help?
And yes - there is a paid library that can do all this. But I would like a freebie. Formats that like not confidential.