Add Events dataset

[jhkennedy]

This:

• Add the Events data to the repository README
• Adds an events/README.md describing the data
• A GitHub Action to automatically copy the events/README.md to the asf-event-data bucket on merges to main
  • The bucket copy of the README will be listed as the dataset documentation in the AWS Open Data catalog, see: https://github.com/awslabs/open-data-registry/pull/...