use cross-env building (#61)

Author: timdeschryver

package.json

@@ -19,7 +19,7 @@
     "url": "https://github.com/storybooks/marksy"
   },
   "scripts": {
-    "build": "BABEL_ENV=production babel src/ --out-dir=lib/ -s",
+    "build": "cross-env BABEL_ENV=production babel src/ --out-dir=lib/ -s",
     "lint": "cross-env NODE_ENV=production eslint --cache --cache-location=.cache/eslint --ext .js,.jsx,.json ./src ./app",
     "prepare": "npm run build",
     "size": "size-limit",