chore: add haarchri to maintainers in OWNERS.md

Signed-off-by: Jared Watts <jbw976@gmail.com>

Author: jbw976

OWNERS.md

@@ -18,6 +18,7 @@ See [CODEOWNERS](CODEOWNERS) for automatic PR assignment.
 * Philippe Scorsolini <philippe.scorsolini@upbound.io> ([phisco](https://github.com/phisco))
 * Jared Watts <jared@upbound.io> ([jbw976](https://github.com/jbw976))
 * Adam Wolfe Gordon <adam.wolfegordon@upbound.io> ([adamwg](https://github.com/adamwg))
+* Christopher Haar <christopher.haar@upbound.io> ([haarchri](https://github.com/haarchri))
 
 ## Reviewers