Add documentation for new currents events and fields

[dulle-braze]

Pull Request/Issue Resolution

Description of Change:

Adding documentation for new events and fields in all Currents connectors.

This can be released with the deploy on Tuesday afternoon (April 9th).

Reason for Change:

Closes #ISSUE_NUMBER_HERE

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PR Checklist

• Ensure you have completed our CLA.
• Tag @EmilyNecciai as a reviewer when the your work is done and ready to be reviewed for merge.
• Consult the Docs Text Formatting Guide to be sure you're utilizing the proper markdown formatting.
• Consult the Docs Writing Style Guide & Best Practices to be sure you're aligning with our voice and other style best practices.
• Preview your deployed changes to confirm that none of your changes break production. Pay close attention to links and images.
• Tag others as Reviewers as necessary.
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[EmilyNecciai]

lgtm!