Update CODEOWNERS

[roypat]

Summary of the PR

As per the e-mail fandree@ sent to the rust-vmm mailing list on 2023/05/02, adding myself as maintainer.

Requirements

Before submitting your PR, please make sure you addressed the following requirements:

• [x] All commits in this PR are signed (with git commit -s), and the commit message has max 60 characters for the summary and max 75 characters for each description line.
• [x] All added/changed functionality has a corresponding unit/integration test.
• [x] All added/changed public-facing functionality has entries in the "Upcoming Release" section of CHANGELOG.md (if no such section exists, please create one).
• [x] Any newly added unsafe code is properly documented.

[andreeaflorescu]

@tkreuzer do you still want to be a maintainer of this crate? I noticed now that you are also listed as a code owner.

[roypat]

Thanks everyone! :)