chore: Adjust build script

Author: sqrtthree

package.json

@@ -25,7 +25,7 @@
   "scripts": {
     "dev": "npm run docs:dev",
     "docs:dev": "vuepress dev docs --no-cache",
-    "docs:build": "vuepress build docs",
+    "docs:build": "npm run docs:clean && vuepress build docs",
     "docs:serve": "serve --single docs/.vuepress/dist",
     "docs:clean": "rm -r docs/.vuepress/dist",
     "lint": "eslint --ext .js,.vue ./",