chore: update vitepress

Author: carwack

package.json

@@ -154,7 +154,7 @@
     "vite-plugin-pages": "^0.9.2",
     "vite-plugin-vue-layouts": "^0.3.1",
     "vite-ssg": "^0.11.4",
-    "vitepress": "^0.12.0",
+    "vitepress": "^0.20.0",
     "vue": "^3.1.4",
     "vue-jest": "^5.0.0-alpha.7",
     "vue-prism-editor": "^2.0.0-alpha.2",