Add rkubis to the opendatahub-io maintainers list

[rkubis]

Description

I am QE of Model Registry, for example @dhirajsb can confirm 😀

New Open Data Hub Member Requirements

• [x] New members have reviewed and acknowledged the Open Data Hub:
  • Code of Conduct
  • Contribution Guide
  • Community Membership Guidelines
• [x] Enabled 2FA on their GitHub account

Pull Request Requirements

• [x] New members are added in alphabetical order
• [x] Only one new member change per commit (if you add two members separate it in two commits
• [x] For individual user changes: Commit message format Add <USERNAME> to <opendatahub-io, mlops-sig, ...>.
• [x] For new team requests: Commit message format Create <TEAMNAME>. If the new team consists solely of existing members, you may
• [x] New GitHub team requests are from an existing opendatahub-io member who will function as the maintainer of the team. Each additional member will follow the same requirements for adding new members

[rkubis]

@anishasthana @accorvin Please, this PR is pending for more than 1 month already.

Let me know if I need to add something before it can be merged.

Thanks!