[BUG] documentation for "encoding" parameter is missing

[Vampire]

I tried to get client-side hashing via the "REST Interface" to work.
I had a hard time (in the end reading the source code) to find out, that I have to give data base64 encoded and addtionally set encoding to BASE64.
I just got as error, that the supplied data length does not match the hash algorithm expected length.
After I have set encoding to BASE64 it started working.
But the only places where it is mentioned is in doc/htdocs/REST_Interface.html as possible request parameter.
But it is nowhere really described and completely missing e.g. from https://docs.keyfactor.com/signserver/latest/plain-signer and https://docs.keyfactor.com/signserver/latest/client-side-hashing.

I think it would be very beneficial to add some words about it to the documentation.