JWT signing with private key & passphrase throws error

Reproduce the example with Node.js v12.20.0, then trace the signing path through jsonwebtoken/sign.js, jwa/index.js, and jws/lib/sign-stream.js shown in the stack trace. The fix is complete when a passphrase-protected PEM private key can sign a PS512 token without the key.key type error, with regression coverage for this case.

Description

Signing jwt token with private key & passphrase results in error. Generated private key as below

ssh-keygen -t rsa -b 2048 -m PEM -f PS512.key and add passphrase

Reproduction

const jwt = require('jsonwebtoken');

const privateKey = `<copy & paste the generated private key here>`;

const token = jwt.sign(
    { test: 12 }, 
    { key: privateKey , passphrase: '...' }, {
    algorithm: 'PS512'
});

console.log(token);

Error

internal/crypto/keys.js:288
      throw new ERR_INVALID_ARG_TYPE(
      ^

TypeError [ERR_INVALID_ARG_TYPE]: The "key.key" property must be of type string or an instance of Buffer, TypedArray, DataView, or KeyObject. Received an instance of Object
    at prepareAsymmetricKey (internal/crypto/keys.js:288:13)
    at preparePrivateKey (internal/crypto/keys.js:308:10)
    at Sign.sign (internal/crypto/sig.js:94:46)
    at Object.sign (jwt-playground/node_modules/jwa/index.js:174:45)
    at Object.jwsSign [as sign] (jwt-playground/node_modules/jws/lib/sign-stream.js:32:24)
    at Object.module.exports [as sign] (jwt-playground/node_modules/jsonwebtoken/sign.js:204:16)
    at Object.<anonymous> (jwt-playground/pem-format-passphrase/jwt-pem-formar-passphrase.js:75:19)
    at Module._compile (internal/modules/cjs/loader.js:999:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1027:10)
    at Module.load (internal/modules/cjs/loader.js:863:32) {
  code: 'ERR_INVALID_ARG_TYPE'
}

Environment

• Version of the library used: 8.5.1
• Version of the Node.js: v12.20.0
• OS: macOS Monterey - 12.6