Update license identifier to conform with SPDX in order to eliminate NPM warning.

Author: enaqx

package.json

@@ -7,7 +7,7 @@
     "Nicholas Schrock <[email protected]>",
     "Daniel Schafer <[email protected]>"
   ],
-  "license": "BSD",
+  "license": "BSD-3-Clause",
   "homepage": "https://github.com/facebook/graphql",
   "bugs": {
     "url": "https://github.com/facebook/graphql/issues"