Update watch scripts

package.json

@@ -20,7 +20,8 @@
     "test:ie": "lerna run test:ie --concurrency 1 --stream",
     "publish": "npm update && npm install && npm run clean && npm run build && lerna publish -m \"Publish\"",
     "update:dependency": "node scripts/update-dependency.js",
-    "watch": "cd jupyterlab && npm run watch"
+    "watch": "watch \"npm run build\" packages --wait 10 --filter=scripts/watch-filter.js",
+    "watch:main": "watch \"npm run build:main\" packages --wait 10 --filter=scripts/watch-filter.js"
   },
   "dependencies": {},
   "devDependencies": {