add @chatton as full codeowner

[colin-axner]

Description

It's my pleasure to add @chatton as a full codeowner. His contributions speak for themselves ❤️

Commit Message / Changelog Entry

type: commit message

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Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• Targeted PR against the correct branch (see CONTRIBUTING.md).
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the module structure standards and Go style guide.
• Wrote unit and integration tests.
• Updated relevant documentation (docs/) or specification (x/<module>/spec/).
• Added relevant godoc comments.
• Provide a commit message to be used for the changelog entry in the PR description for review.
• Re-reviewed Files changed in the Github PR explorer.
• Review Codecov Report in the comment section below once CI passes.

[damiannolan]

Whole heartedly agree as co-conspirator of this initiative ❤️ Thank you @chatton for all of your awesome contributions and here's to many more 🥂

LGTM!

[crodriguezvega]

You deserve it, @chatton! 🥂