Support HS256, HS384 and HS512 signatures in vault config

[overheadhunter]

While HS256 should remain the default signature when writing vault configs, HS384 and HS512 should be accepted when reading a vault config.

Currently, HS256 is hard coded and the algorithm header claim is ignored:

cryptofs/src/main/java/org/cryptomator/cryptofs/VaultConfig.java

Line 186 in 0256d46

var verifier = JWT.require(Algorithm.HMAC256(rawKey)) //