Create Security.md

[GitRon]

User Story

As the maintainer of our packages, I would like to show the world as simply and clearly as possible how we deal with security issues. To do this, it would make sense to remove the contribution part from the (too long) readme and outsource it to a SECURITY.md.

Documentation: https://docs.github.com/en/code-security/getting-started/adding-a-security-policy-to-your-repository

Example: https://github.com/electron/electron/blob/main/SECURITY.md

ACs

• The updater has a SECURITY.md that can be rendered on a project-specific basis
• All packages have been updated