[UR][L0] Add adapter source to codeowners file

Author: kbenzie

.github/CODEOWNERS

@@ -1,5 +1,8 @@
 *                               @oneapi-src/unified-runtime-maintain
 
-# CUDA and HIP plugins
+# Level Zero adapter
+source/adapters/level_zero      @oneapi-src/unified-runtime-level-zero-write
+
+# CUDA and HIP adapters
 source/adapters/cuda            @oneapi-src/unified-runtime-cuda-write
 source/adapters/hip             @oneapi-src/unified-runtime-cuda-write