build: remove old files before building

Author: billyyyyy3320

package.json

@@ -4,8 +4,8 @@
   "description": "Offical blog plugin for VuePress",
   "scripts": {
     "lint": "xo",
-    "dev": "concurrently \"npm:dev:client\" \"npm:dev:node\" \"npm:build:components\"",
-    "build": "concurrently \"npm:build:client\" \"npm:build:node\" \"npm:build:components\"",
+    "dev": "concurrently \"rimraf lib\" \"npm:dev:client\" \"npm:dev:node\" \"npm:build:components\"",
+    "build": "concurrently \"rimraf lib\" \"npm:build:client\" \"npm:build:node\" \"npm:build:components\"",
     "dev:client": "tsc -p tsconfig.client.json --watch",
     "dev:node": "tsc -p tsconfig.node.json --watch",
     "build:client": "tsc -p tsconfig.client.json",
@@ -40,6 +40,7 @@
     "conventional-changelog-cli": "^2.0.1",
     "inquirer": "^6.3.1",
     "nodemon": "^1.18.7",
+    "rimraf": "^3.0.0",
     "ts-node": "^7.0.1",
     "typescript": "3.1.4",
     "vuepress": "^1.0.0"