add build:watch script (#134)

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Co-authored-by: James Daniels <[email protected]>

Author: leoortizz

package.json

@@ -3,6 +3,7 @@
   "private": true,
   "scripts": {
     "build": "./scripts/build.js",
+    "build:watch": "lerna watch -- lerna run build",
     "test": "./scripts/test.js",
     "publish": "./scripts/publish.js",
     "lint": "eslint packages/* scripts/*",