added "watch" script

Author: dmitry-kurmanov

package.json

@@ -3,6 +3,7 @@
   "version": "1.0.36",
   "scripts": {
     "start": "npm run build && live-server",
+    "watch": "webpack --env.buildType dev --watch",
     "prebuild": "webpack --env.buildType dev",
     "build": "webpack --env.buildType prod",
     "release": "standard-version --message \"Release: %s\""