DOP-4352: Set completion time for Netlify builds

[rayangler]

Stories/Links:

DOP-4352

Notes

• The SnootyBuildComplete handler, which is used as a post-build webhook for Gatsby Cloud builds, has been updated to support a query string param called builder. We check if builder has a value of netlify (configured within the Netlify site itself), and update the data we currently need to. We intentionally do not want to notify a user for Netlify builds as they should silently run in parallel. By default, the webhook will assume it's a Gatsby Cloud build and it'll handle any data processing and notifications accordingly. (I thought about creating an entirely different webhook, but I wasn't sure if it was worth introducing having an entirely separate webhook just to have a slight difference. If there's a preference, please let me know!)
• Added an await to the internal db update used in jobRepository.updateExecutionTime. Not having it would cause issues with the post-build webhook where the db connection would close before the update actually occurred.
• For proof of concept, please go to pool_test.queue, filter by {_id: ObjectId('65dcf2d8c78dff69b2b7c74c')}, and see the new netlifyEndTime field added to the end of the document.

README updates

• • This PR introduces changes that should be reflected in the README, and I have made those updates.
• • This PR does not introduce changes that should be reflected in the README

[github-actions]

Your feature branch infrastructure has been deployed!

Your webhook URL is: https://ux3pfecibj.execute-api.us-east-2.amazonaws.com/prod/webhook/githubEndpoint/trigger/build

For more information on how to use this endpoint, follow these instructions.

[mmeigs]

LGTM!