Use Apache-2.0

package.json

@@ -2,7 +2,7 @@
   "name": "echarts",
   "version": "4.2.0-rc.2",
   "description": "A powerful charting and visualization library for browser",
-  "license": "Apache License 2.0",
+  "license": "Apache-2.0",
   "keywords": [
     "visualization",
     "canvas"