max_age defined as string rather than number

[ruiengana]

Describe the bug
In AuthorizationParameters interface max_age is defined as string rather than number.

To Reproduce

<setup client>
const max_age = 86400;
const request = await client.requestObject({
  scope,
  response_type,
  redirect_uri,
  state,
  nonce,
  max_age,
  claims,
  code_challenge,
  code_challenge_method,
});

}

Steps to reproduce the behaviour:

1. Define max_age as number, e.g. 86400
2. Initiate a client and produce a RequestObject with max_age claim

Expected behaviour
Expected RequestObject to accept max_age claim as number.

Environment:

• openid-client version: [v3.15.8]
• node version: [v12.16.2]

Additional context

• the bug is happening on latest openid-client too.
• i have searched the issues tracker on github for similar issues and couldn't find anything related.

[ruiengana]

Thanks!