securityChecks option not available for image scan

[tanguy-platsec]

Hi team,

I was trying to use the recently added security-checks option to remove the secret scanning (enabled by default) because it can cause trivy to timeout on very big images, and by looking at the code, it seems that the option is only being considered for fs and repo types, while it still appears if I do trivy image -h, so I believe it should be available for images too.

I would like to know if there is a reason for this, and I will try to open a pull request in the coming hours.

Thank you for reading me!

[tanguy-platsec]

My PR : #112
My tests : https://github.com/tanguy-platsec/trivy-action-security-checks-option-test/actions