Move executable to cmd directory

[IxDay]

Move executable to cmd directory

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• I've read and agree to the Code of Conduct.
• I've been mindful about doing atomic commits, adding documentation to my changes, not refactoring too much.
• I've a descriptive title and added any useful information for the reviewer. Where appropriate, I've attached a screenshot and/or screencast (gif preferrably).
• I've written tests to cover the new code and functionality included in this PR.
• I've read, agree to, and signed the Contributor License Agreement (CLA).

PR Summary

This patch also allow this repository to be imported in another project.
Only the execution part and config loading is moved to the cmd directory
allowing the use of the core features in other projects.

Related Issues

None for the moment, can open one if needed for traceability.

Test strategy

Keep tests passing as it is only a refactoring.

[awprice]

@nbrownus / @rawdigits / @IxDay
I would love to see this PR merged as it will allow me to use go-audit in a project I am working on. What can we do to get this moving?

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.

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[nbrownus]

👋 @IxDay thanks for the PR, can you do the CLA for us?