chore(package): update prismjs-package to version 0.7.21

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -29,7 +29,7 @@
     "lang-map": "^0.4.0",
     "lodash": "^4.17.2",
     "parse-diff": "^0.4.0",
-    "prismjs-package": "^0.7.20",
+    "prismjs-package": "^0.7.21",
     "react": "^15.4.1",
     "react-dom": "^15.4.1"
   },