Typescript: make type for person.id nullable

[waltjones]

Description of the change

person.id in the Rollbar config should be nullable as documented.

Example:

    payload: {
      person: {
        id: null
      }
    }

This PR makes the Typescript type definition nullable.

Type of change

• Bug fix (non-breaking change that fixes an issue)

Related issues

Fixes #1058

https://app.shortcut.com/rollbar/story/120519

Development

• Lint rules pass locally
• The code changed/added as part of this pull request has been covered with tests
• All tests related to the changed code pass in development

Code review

• This pull request has a descriptive title and information useful to a reviewer. There may be a screenshot or screencast attached
• Issue from task tracker has a link to this pull request
• Changes have been reviewed by at least one other engineer

[dbutts29]

Approved