use correct hash algorithms in PBES2-HS384+A192KW and PBES2-HS512+A256KW

[overheadhunter]

Currently, SHA-256 seems to be hardcoded in the KDF:

jwt-webtool/src/js/app.js

Lines 274 to 278 in 03fd42c

	return jose.JWA.derive(
	"PBKDF2-SHA-256",
	Buffer.from(keyvalue, "utf-8"),
	kdfParams
	);

However, the RFC specifically asks for SHA-384 and SHA-512 respectively, not just different key lengths.

[DinoChiesa]

Ahhh, thank you for the bug report.
Fixed in this commit.