Revert "add sideEffects false for tree-shaking in webpack"

This reverts commit 04038d546aa51179a176fc247d215548d3b6bdfe.

package.json

@@ -5,7 +5,6 @@
   "description": "A browser based code editor",
   "author": "Microsoft Corporation",
   "license": "MIT",
-  "sideEffects": false,
   "scripts": {
     "simpleserver": "gulp simpleserver",
     "release": "gulp release",