Target - Port event reference to github

https://developer.adobe.com/client-sdks/documentation/adobe-target/event-reference/

Note: this document refers to ACP 2.x events, update this doc for latest version and then migrate.

Start with the linked Adobe Target event-reference document and inspect this repository for its corresponding location. Compare the ACP 2.x content with the latest version, then migrate the updated reference into GitHub; done means the current event reference is present and no longer documents the old version.

Written by the indexing model from the issue text.