Add OWNERS in prebuilts/checkstyle

* Owners are selected from top CL approvals or owners.
  They will be suggested to review/approve future CLs.
* OWNERS files are recognized by the new find-owners plugin, see .md files in
  https://gerrit.googlesource.com/plugins/find-owners/+/master/src/main/resources/Documentation/

Test: build/make/tools/checkowners.py -c -v OWNERS
Change-Id: Ifa6dec2b88de198a329521e399a858c718357c57
diff --git a/OWNERS b/OWNERS
new file mode 100644
index 0000000..5af878d
--- /dev/null
+++ b/OWNERS
@@ -0,0 +1,3 @@
+aurimas@google.com
+sergeyv@google.com
+alanv@google.com