Add OWNERS_chromeos files

We are porting this repo to ChromeOS. In order to make the chrome
gerrit accept the ChromeOS UWB team's approval, this CL adds
the ChromeOS UWB team as the owner of this repo.

Bug: 230548624
Test: none
Change-Id: I29e86591a72b3de6d63d31d00a20864e67bd575e
2 files changed