Add OWNERS in external/harfbuzz_ng

* 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: Ia080723b02b0d5e3bc387795e1b371fbd4f4155e
diff --git a/OWNERS b/OWNERS
new file mode 100644
index 0000000..dd9112b
--- /dev/null
+++ b/OWNERS
@@ -0,0 +1,5 @@
+roozbeh@google.com
+behdad@google.com
+siyamed@google.com
+nona@google.com
+jungshik@google.com