Upload Event Types using our new Github Action

The new Upload Event Types to Svix Action is a Github Action that allows users to upload an OpenAPI spec to Svix, automatically creating or updating event types based on the webhooks section of their documentation. This process can be integrated into a CI/CD pipeline to keep event types up to date and in sync with the latest version of the code. The action uses the event type import endpoint provided by Svix API, allowing users to continuously update their event types as they update their OpenAPI spec.