Add life-cycle scripts to update submodules automatically (#165)

Author: fanyang89

package.json

@@ -8,7 +8,8 @@
     "docs:build": "vitepress build",
     "docs:preview": "vitepress preview",
     "lint": "eslint .",
-    "lint:fix": "eslint . --fix"
+    "lint:fix": "eslint . --fix",
+    "prepare": "git submodule update --init --recursive"
   },
   "dependencies": {
     "@theojs/lumen": "workspace:*",