Custom params unsupported by JWT utils types

[JasirZaeem]

The docs suggest nesting any extra params under a custom key, in signed tokens. https://docs.mux.com/guides/secure-video-playback#passing-custom-parameters-to-a-signed-token

{
  "sub": "{PLAYBACK_ID}",
  "aud": "{AUDIENCE_TYPE}",
  "exp": "{EXPIRATION_TIME}",
  "custom": {
    "session_id": "xxxx-123"
  }
}

But the type of params field in the MUXJWTSignOptions does not allow this, necessitating the use of ts-ignore if custom parameters are being used.

mux-node-sdk/src/util/jwt-types.ts

Line 43 in 5b63e5b

params?: Record<string, string>;

Maybe this can be expanded to something more relaxed like params?: Record<string, string | Record<string, string>>; ?

Not the most severe bug but would be a nice QOL improvement.