Add OWNERS file to cmds/uiautomator

* Copied from the androidx.test.uiautomator OWNERS file
  (http://cs/aosp-androidx/test/uiautomator/OWNERS).
* This project is in maintenance mode, and this allows the uiautomator
  team to make occasional fixes as needed.

Test: N/A
Change-Id: If89ced39a77cb55a10cd0608fdc5745462a81ab7