Update docs with steps to upgrade the version in Dotcom

Author: jibrang

Diff for: README.md

@@ -36,6 +36,29 @@ npm install
 npm test
 ```
 
+## Upgrading browser-support in Dotcom 
+
+Before upgrading the browser-support version in Dotcom, we need to ensure that the current functionality is not broken. One of the things that can go wrong is that the functionality to report browser errors to Sentry can break after upgrading this package. Below is a list of steps you can take to ensure this functionality is not broken.
+
+### Review lab testing
+- Create a PR to upgrade the browser-support version in Dotcom.
+- Trigger a browser error from your `review-lab` instance and ensure the error is properly reported in Sentry.
+  - Append the `#b00m` string to your `review-lab` URL and refresh the page.
+  - Verify that the `b00m` error is properly reported in [Sentry](https://github.sentry.io/issues/?environment=review-lab&groupStatsPeriod=auto&project=1890375&query=b00m&referrer=issue-list&statsPeriod=5m).
+  - Run the verification steps in Chrome, Firefox, Edge and Opera browsers. There is an [open issue](https://github.com/github/web-systems/issues/3162) where errors are currently not being reported in Safari browsers.
+
+### Production deployment
+
+- Keep an eye to the `browser-reporting` monitor: https://app.datadoghq.com/monitors/168685099
+- If the rate of browser erorrs reported drops, the monitor will go off and you will get an alert in the [#web-systems-ops](https://github-grid.enterprise.slack.com/archives/C046W1V95FV) channel
+- After the upgrade has deployed to Canary:
+  - Trigger a browser error by appending th e`#b00m` string to your URL.
+  - Verify that the `b00m` error is properly reported in [Sentry](https://github.sentry.io/issues/?environment=canary&groupStatsPeriod=auto&project=1890375&query=b00m&referrer=issue-list&statsPeriod=5m).
+- After upgrade has deployed to production.
+- Trigger a browser error by appending th e`#b00m` string to your URL.  
+  - Verify that the `b00m` error is properly reported in [Sentry](https://github.sentry.io/issues/?environment=canary&groupStatsPeriod=auto&project=1890375&query=b00m&referrer=issue-list&statsPeriod=5m).
+  - Verify the monitor to ensure the rate of reported errors to Sentry has not dropped: https://app.datadoghq.com/monitors/168685099 
+
 ## Contributing
 
 ### Adding polyfills