Link to direct pricing information from readme

[MisterJimson]

Hello. I'm looking into using this project for client side error reporting and wanted to assess the GCP costs of using it.

Looking at the GCP Error Reporting costs here: https://cloud.google.com/stackdriver/pricing#error-report-costs

For the current pricing information, see [Error Reporting Pricing](https://cloud.google.com/error-reporting#pricing).

For limits that apply to your use of Error Reporting, see [Quotas and limits](https://cloud.google.com/error-reporting/quotas).

The first link seems promising and links to here: https://cloud.google.com/error-reporting#pricing

Pricing
Error Reporting supports errors sent through the use of either:

[Cloud Logging](https://cloud.google.com/logging/), which, for pricing purposes, measures the quantity of log data loaded and processed by Logging or other Google Cloud services. See [Pricing](https://cloud.google.com/stackdriver/pricing) for details.
[Error Reporting API](https://cloud.google.com/error-reporting/reference/): you might incur minor Cloud Logging costs if your errors are ingested by Logging. For details, go to [Report error events](https://cloud.google.com/error-reporting/reference#operations).

This is where I get a little lost. Does this project make use of Cloud Logging? If so then the "Cloud Logging pricing summary" at this link should indicate accurate costs I think? https://cloud.google.com/stackdriver/pricing

From the sounds of the readme of this project, it feels like the "Error Reporting API" would more likely be the correct option. The 2 links under that option both go to the same page (https://cloud.google.com/error-reporting/reference/) and it doesn't mention pricing.

Because of the above, I am unable to assess the costs of using stackdriver-errors-js in my project.