add several helper npm scripts to manage all packages

Author: Salakar

package.json

@@ -6,6 +6,9 @@
   "scripts": {
     "format": "prettier --write {,**/}*.{yaml,js,md}",
     "test": "prettier --list-different {,**/}*.{yaml,js,md}",
+    "extensions:clean": "lerna run clean",
+    "extensions:build": "lerna run build",
+    "extensions:test": "lerna run test",
     "postinstall": "lerna bootstrap"
   },
   "repository": "",