docs: add asf notice

Ovilia · Ovilia · commit 5a0b7f68ba8d · 2018-04-23T11:25:15.000+08:00
diff --git a/NOTICE b/NOTICE
@@ -0,0 +1,5 @@
+Apache ECharts (incubating)
+Copyright 2017-2018 The Apache Software Foundation
+
+This product includes software developed at
+The Apache Software Foundation (http://www.apache.org/).
