[owners] Adding OWNERS to doc_checker tool

This tool is used to validate various parts of
the documentation in //docs.

Change-Id: Ic05f226cf5724a16115e1572a8964c2c2960b6fb
diff --git a/tools/doc_checker/OWNERS b/tools/doc_checker/OWNERS
new file mode 100644
index 0000000..2c9ca87
--- /dev/null
+++ b/tools/doc_checker/OWNERS
@@ -0,0 +1,3 @@
+ccherubino@google.com
+mangini@google.com
+wilkinsonclay@google.com