* Export rating thresholds for all Web Vitals, add `MetricRatingThresholds` type
* Add node:test runner and unit tests for API exports
* Add getMetricRatingThresholds(), refactor typeMetricRatingThresholds
- Replace exported Web Vitals metric thresholds with a new public
function`getMetricRatingThresholds()`
- Refactor `MetricRatingThresholds` type to be more self-explanatory
* Revert to original implementation
* Mv 'Rating Thresholds' before 'Attribution' in README, add recommendation note
Rob McGuire