Added `browser` field to the package.json

package.json

@@ -15,6 +15,7 @@
     "node": ">=6.11.5"
   },
   "main": "dist/index.js",
+  "browser": "dist/index.browser.js",
   "bin": {
     "javascript-obfuscator": "./bin/javascript-obfuscator"
   },