chore(npm): add the license to package.json

This removes a warning when executing npm install.

Closes angular#12111

Author: realityking

package.json

@@ -1,5 +1,6 @@
 {
   "name": "angularjs",
+  "license": "MIT",
   "branchVersion": "^1.4.0-beta.0",
   "branchPattern": "1.4.*",
   "repository": {