update_engine: Install payload signing public key

BUG: 23937688
Change-Id: I931a196e207643077185b7bc904744cd42f82c32
diff --git a/update_payload_key/brillo-update-payload-key.pub.pem b/update_payload_key/brillo-update-payload-key.pub.pem
new file mode 100644
index 0000000..7e5164c
--- /dev/null
+++ b/update_payload_key/brillo-update-payload-key.pub.pem
@@ -0,0 +1,9 @@
+-----BEGIN PUBLIC KEY-----
+MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAxAxPqfII4vIe3cqKzdvl
+gwjBhj9kyF+6ig73yZq0o4wLOq3nsRUToaIOtQmcjr1G+hhSXBU3WTbfZLlm07Fb
+B535o2zhYghs8Br7xobjX+gikEnxnFuTtB2sB4Gpan4hKwU+BuZhJDSl1oZwUJJ4
+eiGJpH5xJswbyO/bA81BCMjU3rm+G6SzOLQTK0YEnhn7bB69UucM57GM7l+dCl8r
+RhKjbpP7E1fVtgX++BGs6pKciPLxYfXVup0MgH0h8VdSDMiHkshIXYvcCV1KOBFX
+9GrYvXLtq41Hm5hC5l48mwLi0ALdIfbPQ5oHLl2u+etLmGwbMpzhybTCZQA/SgEl
+HwIDAQAB
+-----END PUBLIC KEY-----