Establish a security process

We should create a well defined, step-by-step process on how to deal with security issues.
A good example from a project I contributed to is from libssh:

https://www.libssh.org/development/security-process/

Start by reviewing the linked libssh security process and inspect rust-keylime’s existing security or contribution documentation. Done means this project has a clear, documented, step-by-step process for handling security issues, adapted from the example rather than copied without project-specific context.

Written by the indexing model from the issue text.