Add Igor Frenkel as maintainer of security report schemas project

Manager Justification

It's hard to specify hard requirements for becoming a maintainer, which is why the documentation consists of flexible guidelines. Reviewers are encouraged to think of their eligibility for maintainership in the terms of "I could be ready at any time to be a maintainer as long as my work as an author and reviewer is consistent with other maintainers".

• The MRs reviewed by the candidate consistently make it through maintainer review without significant additionally required changes.
• The MRs authored by the candidate consistently make it through reviewer and maintainer review without significant required changes.

List of contribs

• added dangerbot to project
• added ajv strict mode to project
• was one of the initial contributors to the security report schemas project early on

Before Merging (Manager Tasks)

• Mention the maintainers from the given specialty and ask them to provide feedback to the manager directly.
• Leave this merge request open for 1 week, to give the maintainers time to provide feedback.
• Ensure we have at least 2 approvals from existing maintainers.

Once This MR is Merged

1. Ask for maintainer access to gitlab-org/security-products/security-report-schemas/
2. Add yourself to the CODEOWNERS file in the project
3. Announce it everywhere
4. Keep reviewing, start merging 🤘 😎 🤘