Create ESM builds (#6)

Author: wojtekmaj

.babelrc

@@ -1,5 +1,10 @@
 {
-  "presets": [
-    "@babel/env"
-  ]
+  "presets": ["@babel/env"],
+  "env": {
+    "production-esm": {
+      "presets": [
+        ["@babel/env", { "modules": false }]
+      ]
+    }
+  }
 }

package.json

@@ -2,10 +2,14 @@
   "name": "detect-element-overflow",
   "version": "1.1.1",
   "description": "A function that tells you whether a given element is overflowing its container or not. Useful for creating dropdowns and tooltips.",
-  "main": "dist/index.js",
-  "es6": "src/index.js",
+  "main": "dist/umd/index.js",
+  "module": "dist/esm/index.js",
+  "source": "src/index.js",
+  "sideEffects": false,
   "scripts": {
-    "build": "babel src -d dist --ignore **/*.spec.js",
+    "build": "yarn build-esm && yarn build-umd",
+    "build-esm": "BABEL_ENV=production-esm babel src -d dist/esm --ignore **/*.spec.js",
+    "build-umd": "BABEL_ENV=production-umd babel src -d dist/umd --ignore **/*.spec.js",
     "clean": "rimraf dist",
     "lint": "eslint src/ --ext .jsx,.js",
     "prepublishOnly": "yarn clean && yarn build",