workflow: support "yarn register-vuepress"

Local development will benefit from it.

Author: ulivz

package.json

@@ -13,6 +13,7 @@
     "build": "yarn workspace docs build",
     "dev:blog": "yarn workspace blog dev",
     "build:blog": "yarn workspace blog build",
+    "register-vuepress": "lerna exec --scope vuepress -- yarn link",
     "lint": "eslint --fix packages/**/*.js packages/**/*.vue packages/**/bin/*",
     "release": "yarn --pure-lockfile && node scripts/release.js",
     "changelog": "node scripts/genChangelog.js run",