Add system-wide cron job analytic rule

[nusantara-self]

This PR adds an analytic for system-wide cron job changes detection, which is not covered by default analytics in JAMF Protect.

[txhaflaire]

Hi @nusantara-self

Thanks for the contribution to this repository, we are going to review the PR as soon as possible.
Feel free in meantime to add any screenshots from the captured alerts during your testing here as well.

Cheers,
Thijs

[nusantara-self]

Hello @txhaflaire,

Thanks a lot! Here's an example screenshot showing what the alert looks like. Without this custom rule, a direct change to /etc/crontab would go unnoticed / would not trigger an alert.

Cheers,
Fabien