Add OWNERS in tools/apksig

Owners are selected from top CL approvals or owners.
They will be suggested to review/approve future CLs.

Test: default make
Change-Id: Id505e535ce93da0952e33d479006f603e9919d56
diff --git a/OWNERS b/OWNERS
new file mode 100644
index 0000000..0b8d398
--- /dev/null
+++ b/OWNERS
@@ -0,0 +1,2 @@
+cbrubaker@google.com
+klyubin@google.com