es builds

packages/splitjs/package.json

@@ -4,6 +4,7 @@
   "description": "2kb unopinionated utility for resizeable split views",
   "main": "dist/split.js",
   "minified:main": "dist/split.min.js",
+  "module": "dist/split.es.js",
   "repository": "https://github.com/nathancahill/split",
   "keywords": ["css", "split", "flexbox", "tiny", "split-layout"],
   "author": "Nathan Cahill <nathan@nathancahill.com>",

packages/splitjs/rollup.config.js

@@ -14,7 +14,14 @@ const output = {
 export default [
     {
         input: 'src/split.js',
-        output,
+        output: [
+            output,
+            {
+                file: pkg.module,
+                format: 'esm',
+                sourcemap: false,
+            },
+        ],
         plugins: [buble()],
     },
     {