fix serve command

Author: VincentRPS

package.json

@@ -16,7 +16,7 @@
     "swizzle": "docusaurus swizzle",
     "deploy": "docusaurus deploy",
     "clear": "docusaurus clear",
-    "serve": "docusaurus serve",
+    "serve": "yarn build && docusaurus serve",
     "write-translations": "docusaurus write-translations",
     "write-heading-ids": "docusaurus write-heading-ids",
     "typecheck": "tsc"