chore(package.json): add sideEffects entry (#62)

See https://webpack.js.org/guides/tree-shaking/#mark-the-file-as-side-effect-free

Author: avocadowastaken

package.json

@@ -2,6 +2,7 @@
   "name": "react-apollo-hooks",
   "version": "0.3.0",
   "description": "",
+  "sideEffects": false,
   "main": "lib/index.js",
   "module": "es/index.js",
   "typings": "lib/index.d.ts",