docs(security): update

[fredcerdrak]

Describe your changes

The security docs are outdated. It states Axis does not have a bug bounty program, which is false? And there's a dead link to the vulnerability policy.

In this draft I simply replaced all information with a proper link to the policy (which includes everything you need to know).

Perhaps the "overview" part could be included in this document as well? Or it should be a clone of the policy (i.e. duplicate all information from the policy).

Checklist before requesting a review

• I have performed a self-review of my own code
• I have verified that the code builds perfectly fine on my local system
• I have added tests that prove my fix is effective or that my feature works
• I have commented my code, particularly in hard-to-understand areas
• I have verified that my code follows the style already available in the repository
• I have made corresponding changes to the documentation