Feature: Ignore select GitHub webhook events

[Collinbrown95]

Description

Github fires a lot of distinct webhook events associated with simple actions (e.g. when testing locally a single commit triggered around 20 webhooks).

It would be nice if the webhook server checked up front so that only important events such as commits to the main branch or deploys create messages in the NATS queue.

The rationale for this feature is to avoid many duplicate work items being created in rapid succession since every webhook event creates scans by default.