Add FAQ on reporting security bugs

[jeffpaul]

Description of the Change

This pull request adds a new FAQ section to both the README.md and readme.txt files, providing instructions on how to report security bugs for the ElasticPress Debugging Add-On plugin.

Documentation updates:

• Added a "Frequently Asked Questions" section to README.md with guidance on reporting security vulnerabilities through the Patchstack Vulnerability Disclosure Program.
• Added a corresponding FAQ entry to readme.txt with the same security reporting instructions.

How to test the Change

Changelog Entry

Developer - Add Patchstack security-reporting FAQ.

Credits

Props @jeffpaul.

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added Critical Flows, Test Cases, and/or End-to-End Tests to cover my change.
• All new and existing tests pass.

[jeffpaul]

@felipeelia note that I think we need to get these changes to WPORG for them to take effect in Patchstack's VDP, so I'll keep an eye out here for the next release and will trigger the Patchstack VDP confirmation on their end for this plugin then

[felipeelia]

Thanks @jeffpaul. We already have a couple of things that are worth a new release (probably 3.1.2 instead of 3.2.0 though), so it won't take us long to have a new version available.