Add module entry. Related rollup/rollup-plugin-node-resolve#48.

mbostock · mbostock · commit 3da261a5e108 · 2016-08-02T14:47:14.000-07:00
diff --git a/package.json b/package.json
@@ -19,6 +19,7 @@
     "url": "http://bost.ocks.org/mike"
   },
   "main": "build/d3-force.js",
+  "module": "index",
   "jsnext:main": "index",
   "repository": {
     "type": "git",
