refine "prepublishOnly" script

Author: jay-es

package.json

@@ -9,7 +9,7 @@
   ],
   "scripts": {
     "prepare": "husky install",
-    "prepublishOnly": "npm run build",
+    "prepublishOnly": "git diff HEAD --exit-code && npm run build",
     "prebuild": "node -e \"fs.rmSync('lib/', { recursive: true, force: true })\"",
     "build": "tsc",
     "format": "prettier --check ./**/*.[jt]s",