add authors file

AUTHORS

@@ -0,0 +1,9 @@
+# This is the list of coix's significant contributors.
+#
+# This does not necessarily list everyone who has contributed code,
+# especially since many employees of one corporation may be contributing.
+# To see the full list of contributors, see the revision history in
+# source control.
+Google LLC
+Du Phan
+Heiko Zimmermann