Prevent various unneeded files from being part of the npm package

This specifically fixes issues with React Native because of the presence
of a .babelrc in the npm package.

As seen in amplitude#32

package.json

@@ -25,6 +25,10 @@
     "type": "git",
     "url": "https://github.com/amplitude/redux-query.git"
   },
+  "files": [
+    "dist",
+    "src"
+  ],
   "keywords": [
     "redux",
     "react",