Allow rollbar instance from alternate import/require

[waltjones]

Description of the change

The Provider validates the Rollbar instance, when one is in the props, by testing instanceof the default Rollbar import. This fails when the instance was constructed from another import or require. The specific issue report involves using the noconflict bundle.

This PR looks for an initialized options object instead. This will successfully catch common errors like passing the constructor function or failing to initialize before passing the instance.

Type of change

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

Related issues

Fixes https://github.com/rollbar/rollbar-react/issues/24

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
• [ ] "Ready for review" label attached to the PR and reviewers assigned
• [ ] Issue from task tracker has a link to this pull request
• [ ] Changes have been reviewed by at least one other engineer